Costco and Sam's Club are the leading warehouse club rivals for bulk buying.
The warehouse chains' respective in-house brands are where the savings can really add up.
We compared the prices of Costco's Kirkland Signature items with matching Sam's Club Member's Mark items.
The world of warehouse retail has two top titans: Costco and Sam's Club.
The chains have a lot in common.
Indeed, they each trace their roots to Sol Price, who mentored a Costco cofounder and inspired Walmart's Sam Walton to launch his own version of the concept.
Both clubs charge an annual membership fee ($65 at Costco, $50 at Sam's) that allows shoppers to peruse spartan aisles stacked with pallets of bulk-packaged goods at bargain prices.
Another similarity is that each one carries products under their own in-house labels, Kirkland Signature at Costco, and Member's Mark at Sam's.
And these private-label offerings have earned loyal followings among their customers.
To find out which side offers the best value, we visited locations in Wisconsin to compare prices on a dozen common household items.
We focused on functionally similar products, though some exact matches were not available.
In general, we found Costco had a broader selection in its Kirkland line. Of 17 Kirkland items we looked at, we found appropriate matches for only 12 from Member's Mark.
On the other hand, Member's Mark included a few more economical options. For example, Kirkland Signature sometimes offered only an organic option, which was often more expensive.
After adjusting for pack size, the 12 items from Sam's Club totaled $150, while the Costco products totaled $158.
Here's how each item contributed to the cart totals.
Sugar — Member's Mark
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Costco's bulk sugar option is organic cane sugar, priced at $12 for a 10-pound bag. Member's Mark offers similar-sized bags of white granulated sugar for less than $7.28 — a savings of nearly $5. (If you need 10 pounds of sugar, that is.)
Winner: Sam's Club
Laundry detergent — Member's Mark
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Member's Mark laundry detergent sells for about $3 less per jug than the comparable Kirkland Signature option.
Winner: Sam's Club
Chicken nuggets — Member's Mark
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As with sugar, the Costco option is organic, about $2 more than these Member's Mark nuggets at Sam's Club.
Winner: Sam's Club
Facial tissue — Member's Mark
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A dozen boxes of Kirkland Signature facial tissue cost $1 more than the same quantity of Member's Mark facial tissue.
Winner: Sam's Club
Cheese blocks — TIE
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Kirkland Signature sharp cheddar cheese costs $0.24 more than the Member's Mark colby jack cheese. Since they are technically different styles of cheese and within 5% of each other on price, we're calling this a tie.
Winner: Tie
Pain and fever medication — TIE
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The Member's Mark acetaminophen is about $0.50 cheaper than the Kirkland Signature version, but that is less than a 4% difference in the total.
Either way, both options cost about half as much per gel cap as Tylenol.
Winner: Tie
Dish soap — TIE
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This Kirkland Signature dish soap is $0.089 per ounce, a tenth of a penny less than the unit price of the Member's Mark option. That works out to an $0.11 advantage to Costco.
Winner: Tie
Allergy medication — TIE
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Allergy meds are among the most cost-effective products to buy from a warehouse club's private-label brand.
The Kirkland Signature version of Zyrtec costs a fraction of a cent less per tablet than Member's Mark, but both of those are about 89% less than the name-brand option.
Winner: Tie
Snack bars — TIE
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Kirkland Signature and Member's Mark have similar nutty snack bars to those sold by Kind. After adjusting for pack size, the Costco option is about $0.50 less than Sam's Club, but that's still less than a 5% difference in price.
Winner: Tie
Batteries — Kirkland Signature
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A Kirkland Signature battery costs $0.35, while a similar Member's Mark battery is $0.02 more, or about 5.5%.
Winner: Costco
Bottled water — Kirkland Signature
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40-packs of bottled water cost $0.30 less at Costco than at Sam's Club. That's a seemingly small number, but it works out to a price difference of nearly 7%.
Winner: Costco
Whole bean coffee — Kirkland Signature
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Both clubs sell their own versions of Colombian Supremo beans. The Kirkland Signature price is about $0.64 per pound less than the Member's Mark price. That's a savings of about 8%.
Both options are less expensive than the beans available at the warehouses from Starbucks.