Costco's October book opens tomorrow, a $7.96 magnesium at its floor, and Vitacost's Sept. 21 cutoffs (2026)

Prices were checked at 9:10 a.m. ET on Sunday, Sept. 20, 2026, across Costco, Amazon, iHerb, Vitacost and Walmart.

Costco's member savings book turns over tonight: the August–September book ends at warehouse close today, and the October book opens Monday and runs through Oct. 18. Amazon supplies this week's two best-documented prices — a $7.96 magnesium that has reached $7.95 on the deal community's front page twice, and a $759.99 smith machine whose own posted history shows $650.

At a glance

Retailer	Item or promotion	Current price	Price math	Deadline and checks	Price status
Costco	October member book opens · Liquid I.V. Hydration Multiplier · 30 ct	$20.99	$28.99 warehouse price − $8.00 instant savings	Runs Sept. 21–Oct. 18; limit 4; warehouse, online and location prices can differ	Current book price; no published price series 1
Amazon	Nature Made Zinc · 30 mg, 100 ct, quantity 2	2 for $3.08	$9.98 two-pack − $2.00 clipped coupon − $4.40 multibuy − $0.50 Subscribe & Save	Select accounts; clip coupon, add quantity 2, check out with Subscribe & Save; free shipping with Prime or $35+	Front-page verified stack; all-time low unverified 2
Amazon	VitBoost Magnesium Glycinate · 500 mg, 120 ct	$7.96	$9.95 − 20% clipped coupon; 5% Subscribe & Save takes it to $7.46	Select accounts; the coupon's own availability sets the window	At a documented floor: $7.95 on the front page twice before 3
Amazon	Force Factor Creatine Monohydrate · 1 kg	$11.99	$19.99 − $6.00 clipped 30% coupon − $2.00 Subscribe & Save	Select accounts; one use per coupon; confirm the $6 shows in your cart	$5.43/lb; editors measured it $8 under the next best merchant 4
Amazon	Vitamin Bounty Multi Collagen · 28 servings	$11.99	$23.99 − $9.60 clipped 40% coupon − $2.40 Subscribe & Save	A further 10% brand coupon drops some accounts to $9.59; free shipping with Prime or $35+	50% off list; the serving is about half the size of Orgain or Vital Proteins 5
iHerb	NAD+ supplements with code `NADPLUS30`	30% off	Applied at checkout; CGN NRT 250 mg lands at $11.48	Ends Tuesday, Sept. 22, 1:00 p.m. ET; one use, one unit per SKU; free shipping at $30, otherwise $6 flat	Official code; item-level price histories unlisted 6
Vitacost	Brand tiers at 15%, 20% and 25% off	Varies by product	Automatic at checkout, no code	Most tiers end Monday, Sept. 21, 7:00 a.m. ET; three run to Sept. 28	Official promotion; product-level prices and histories unlisted 7
Walmart	Mikolo Smith Machine Home Gym	$759.99	Listed at $1,500; sold and shipped by Mikolo Fitness; free shipping	Check the seller panel before paying	Above its floor: $650 twice, $700 and $800 in 2025, $770 in June 8

Costco: the book turns over tonight

Two Costco events land on the same weekend. The current member book ends, and next month's begins.

The Aug. 24–Sept. 20 book prices Vital Proteins Collagen Peptides, 24 ounces unflavored, at $23.99 after a $6 manufacturer saving, limited to three units. The October pages list a youthéory Versisol Collagen at $9 off in its place. 1 9

Slickdeals Daily has posted the October member book pages, which cover Sept. 21 through Oct. 18. The book runs more than 35 health and personal-care rows, and it prints them in two different formats — a few pages show the full warehouse price, the instant savings and your cost, while the supplement pages show the savings amount on its own. 1

Only two rows in the health aisles carry a complete price comparison:

Liquid I.V. Hydration Multiplier, 30 packets, sugar-free Ring Pop Cherry or White Peach Raspberry Lemonade: $28.99 less $8.00, or $20.99. Limit four.
Ensure Original Nutrition Shake, vanilla, 30 × 8 fl oz: $37.49 less $8.50, or $28.99, which is 97 cents a shake. Limit six.

The rest of the supplement pages state a dollar saving with no shelf price. Grouped by what you would be buying:

Nature Made — CoQ10 90 ct $8 off; CholestOff Plus 210 ct $5.50 off; Magnesium Citrate 180 ct $4.50 off; Super B-Complex 460 ct $4 off; Iron 365 ct $2.50 off; Super C 200 ct, Extra Strength C gummies 180 ct, Vitamin D3 650 ct and D3 gummies 200 ct all $3.50 off. Limit 15 each.
Sports Research — Magnesium L-Threonate 135 ct $7 off; Omega-3 Fish Oil 150 ct and L-Theanine 150 ct $6 off each. Limit 15 each.
Qunol — Liquid CoQ10 and Liquid Turmeric, 30.4 fl oz, $10 off each. Limit 15 each.
youthéory — Total Body Turmeric 90 ct $10 off; Versisol Collagen 345 ct $9 off; Ashwagandha 180 ct $6 off. Limit 5 each.
Kirkland Signature — Fish Oil 400 ct $3.50 off; Extra Strength Energy Shot 48 ct $8 off; Severe Cold & Flu 112 ct with Night 56 ct $3 off.
Nature's Bounty — B-12 300 ct and Sleep3 Melatonin 120 ct $5 off each; Hair, Skin & Nails 250 ct and Immune 24 Hour+ $4 off each; Zinc 400 ct $2.50 off.
Centrum — Silver Men 50+ and Silver Women 50+ Multi, 275 ct, $4.50 to $6 off.
Others — Glucerna Shake 24 × 8 fl oz $10 off; Neuriva Brain 50 ct $10 off; Force Factor Hair Growth Accelerator 90 ct $7 off; Emergen-C Immune+ variety 90 ct, Culturelle Digestive Daily 80 ct, Osteo Bi-Flex Triple Strength 300 ct and Bausch + Lomb PreserVision AREDS 2 210 ct all $6 off; Estroven Complete 84 ct $5 off; Airborne Effervescent 2/18 ct and OllY Kids, Men's, Women's and Sleep multis $3.50 to $4 off.

Costco prints those limits item by item, and most of the supplement rows cap at 15. The page also warns that warehouse pricing can differ in Alaska, Hawaii, Puerto Rico, Business Centers and online, so the shelf tag at your local store is the number that counts. 1

Protein, creatine and collagen

Amazon: Force Factor Creatine Monohydrate, 1 kg for $11.99

Amazon lists the unflavored 2.21-pound tub at $19.99. Clipping the 30% coupon on the product page and checking out with Subscribe & Save brings the total to $11.99, which is $5.43 a pound, or about 6 cents per 5-gram serving. The post carries a +208 community score and 52,900 views, and Slickdeals' editors measured it $8 below the next best reputable merchant. 4

Two account-level checks decide whether you get this price. Commenters report that the 30% coupon shows on some logins and not others, and one buyer saw only $2 come off. Check your own cart total before paying. 4

The labelling deserves a second look too. The tub says made in the USA, and commenters point out that Force Factor sources its raw creatine from international manufacturing hubs. Buyers who care about third-party certification should read the ingredient panel before ordering. 4

Amazon: Vitamin Bounty Multi Collagen, 28 servings for $11.99

The stack runs from a $23.99 list price: a $9.60 clipped coupon, then $2.40 off through Subscribe & Save. Some accounts see an additional 10% brand coupon that takes the tub to $9.59. 5

At $11.99 for 28 servings the cost is about 43 cents a serving. A commenter raised the catch: this brand's serving carries roughly half the collagen and protein that Orgain or Vital Proteins put in theirs, so the fair comparison is cost per gram of collagen, and this tub wins on paper by a smaller margin than the headline suggests. 5

Costco: Ensure Original, 30 shakes for $28.99

The October book covers the ready-to-drink side of the category. Ensure Original in vanilla, 30 bottles of 8 fluid ounces, drops from $37.49 to $28.99 with the $8.50 instant saving. The limit is six cases, and the book runs to Oct. 18. 1

Protein powder: bars, creatine and collagen this week

The community's supplement section ran protein bars, creatine and collagen this week. A bulk whey isolate or concentrate at or below the $10-to-$11-a-pound benchmark that earlier scans used did not appear. iHerb's own deals page carried no standalone protein powder either. 10 11

Vitamins and supplements

Amazon: Nature Made Zinc, two bottles for $3.08

This is the deepest stack in the scan, and it needs four steps in order. Buy two bottles at the two-for-$9.98 price, clip the 40% coupon on the product page, let Amazon's multibuy discount take another $4.40, then check out with Subscribe & Save for the final $0.50. The total lands at 2 for $3.08, or $1.54 a bottle. 2

Each bottle is 100 tablets of 30 mg zinc, a 100-day supply at one tablet a day, so the two-bottle order covers most of a year. Slickdeals' editors measured the deal $6.90 below the next best reputable merchant, and the post reached the front page with 8,100 views. The price applies to select accounts, and the coupon is usually single-use. 2

Amazon is also running $10 off a $40 spend on selected health and beauty items, which can layer on top of an order like this one. The examples Slickdeals listed were personal-care products, so watch the promo tag appear in your cart before counting on it. 12

Amazon: VitBoost Magnesium Glycinate, 120 capsules for $7.96

Amazon lists the 500 mg capsules at $9.95, and the 20% on-page coupon takes the price to $7.96. Subscribe & Save pulls it to $7.46. 3

This one carries a price history, which is rare in this category. The same item has hit $7.95 on the front page twice before, once with a 443 deal score and 79 comments, and once with 462 and 116 comments. 13 14

So $7.96 sits one cent above the lowest price this product has been posted at. That makes it the closest thing to a confirmed floor in this week's scan. The current post's own score is -1, which signals thin voting. The two earlier posts are what establish the level. 3

iHerb: 30% off NAD+ supplements with code NADPLUS30

iHerb has opened a category discount on NAD+ products: 30% off eligible items with promo code NADPLUS30, through Tuesday, Sept. 22 at 1:00 p.m. ET. The code is good for one use, covers one unit per SKU, and shipping is free on orders of $30 or more — below that, flat-rate shipping costs $6. 6

Three prices worth checking against the code:

California Gold Nutrition NRT 250 mg, 60 veggie capsules — $11.48
Thorne ResveraCel, 60 capsules — $42.00
ProHealth Longevity NMN Pro 1000, 60 capsules — $45.46

iHerb's own deals page is worth a separate look this week. It carried no standalone protein powder, and its supplement listings were shorter than usual: Natrol Melatonin Gummies at $21.66, Natrol Biotin at $15.59, True Sea Moss gel at $34.99 with 30% off in cart, and California Gold Nutrition Baby's DHA at $8.66 against a $17.33 reference. 11

Home fitness equipment

Walmart: Mikolo Smith Machine Home Gym at $759.99

Walmart lists the Mikolo smith machine with a cable crossover, weight bar, landmine and barbell holders at $759.99, sold and shipped by Mikolo Fitness, with free shipping. The post displays a $1,500 list price, and that figure is where the 49% off badge comes from. 8

Slickdeals keeps a price panel for this exact machine, and it shows what the rack has actually sold for:

$650, twice — December 2025 and April 2026, both front-page posts
$700 in November 2025
$770 in June 2026
$800 in November 2025

Today's $759.99 therefore sits $110 above the lowest posted price for this product, and roughly in line with where it has traded for most of the past year. 8

Two comments worth reading before buying. One buyer found the same machine unbranded on Temu for about $633, and another points out that Mikolo's newer M11 version ships with more attachments at the same price. Both sit in the thread linked above. 8

Equipment stayed thin again this week. The supplement section produced the volume; a walking pad, a treadmill or an adjustable dumbbell set at a genuinely competitive price did not turn up in this scan. 10

Retailer-wide promotions and expiry cliffs

Vitacost: every brand tier ends Monday morning

Vitacost's current automatic discounts apply in the cart while supplies last, and nearly all of them share one deadline. 7

Ending Monday, Sept. 21 at 7:00 a.m. ET:

25% off — Vitacost's own brand, Rise Bar, Om Mushrooms, CRYSTAL, Great Lakes Wellness, Nutri, Organic India, Sunfood, and selected on-the-go bars and snacks
20% off — Kiss My Face, selected vegan and plant-based items, Wiley's Finest, Further Food, Nutrex Hawaii, Zesty Paws
15% off — Double Wood Supplements

Running to Monday, Sept. 28 at 7:00 a.m. ET: 25% off OceanBlue, and 20% off Tribe Organics and Mariani.

Two names on that list matter more than the rest for this channel. Great Lakes Wellness is a collagen brand, and Wiley's Finest is a fish-oil brand, so a 25% or 20% tier is where a supplement restock can land at its best price of the quarter. Standard shipping is free on Vitacost orders over $30. 7

The page shows brand-level percentages and nothing at the product level. A 25% off label tells you what will change at checkout, so check the base price on the specific bottle before you build a cart around one. 7

iHerb

The NAD+ code is the live iHerb offer this week. It expires Tuesday at 1:00 p.m. ET, and the free-shipping threshold sits at $30. 6

Checkout order and expiry watch

Today, at Costco. Vital Proteins Collagen Peptides, 24 oz, at $23.99 after $6 off, limit 3. The book ends at warehouse close, and October's pages carry no Vital Proteins collagen. 1 9
Tonight, at Vitacost. Build any cart that depends on the 15%, 20% or 25% brand tiers. The deadline is 7:00 a.m. ET Monday, which is before most people shop. 7
Today, at Amazon — the zinc stack. Clip the 40% coupon, add a quantity of two, apply Subscribe & Save, and confirm $1.54 a bottle in the cart before paying. 2
Today, at Amazon — the magnesium. Clip the 20% coupon for $7.96, or take $7.46 with Subscribe & Save. This is the one price in this issue sitting a cent above a documented floor. 3
Today, at Amazon — creatine and collagen. Enter the coupon codes on both product pages, verify the discount registered, then switch to Subscribe & Save for the final step. Both prices depend on coupons that appear on some accounts only. 4 5
By Tuesday, 1:00 p.m. ET, at iHerb. Apply NADPLUS30 and check that the 30% registers on a single unit per SKU. 6
Whenever the machine can wait, at Walmart. The Mikolo smith machine at $759.99 sits $110 above its own posted low of $650, which has come around twice in ten months. 8

How to read the labels in this issue

Two offers here come with a checkable price history, and both are named in the sections above: the VitBoost magnesium at $7.96 against two prior front-page prices of $7.95, and the Mikolo smith machine at $759.99 against a posted low of $650. Those two carry a real comparison to what the product has sold for.

Every other entry rests on a current comparison that the seller supplies — Costco's warehouse price against its own list price, Vitacost's brand-level percentage, iHerb's category discount, or Slickdeals' editors measuring one merchant against the next best. Those figures tell you what changed this week. 1 6 7