Walmart and Costco Aren't Competing. They Never Were.

Costco and Walmart get treated like the same kind of business. They are not. They make money in almost opposite ways, which is exactly why both have absorbed years of inflation and tariffs without breaking the promise that brought their customers in.

Walmart's everyday-low-price strategy depends entirely on volume and supplier leverage. A typical Walmart Supercenter stocks over 100,000 SKUs and uses that scale, plus a cross-docking logistics network refined over decades, to squeeze suppliers on cost and pass a sliver of the savings forward. The margin comes from selling an enormous amount of almost everything, at a thin markup, to almost everyone. When tariffs raise input costs, Walmart's leverage over thousands of suppliers gives it room to absorb part of the hit before shelf prices have to move at all. Walmart is also extending the model: global e-commerce sales grew 27% in its most recent quarter, and Walmart+ — its membership tier — has reached 18.4 million subscribers, adding a stickiness layer the everyday-low-price model alone could never generate.

Costco doesn't really compete on that axis. It carries only 3,500 to 4,000 SKUs per warehouse — a fraction of Walmart's range — and caps merchandise margins around 14 to 15%, intentionally near breakeven. The actual profit engine is the membership fee. Fee income alone jumped 14% year over year recently, comfortably beating analyst expectations, while renewal rates hold at 89.7% worldwide even after price increases. Costco doesn't need every item to carry a profit, because the relationship was never with the product. It's with the member who already paid to walk through the door.

That structural difference is what lets each absorb a tariff shock differently. Walmart spreads the cost across volume and supplier negotiation, leaning on scale most competitors simply cannot match. Costco spreads it across a fee its members have already shown, repeatedly, they will pay even as it rises — and its private label, Kirkland Signature, now representing 32 to 35% of total Costco sales, gives it a cost lever that Walmart's house brands don't quite match at the same scale.

Neither company is winning a price war with the other, because they were never playing the same game. One sells a platform to brands. The other sells trust to households. The lesson for a founder isn't "compete on price." It's that the customer relationship you actually build — pay once and trust the system completely, or compare every single item every visit — is what determines which costs you can quietly absorb later and which ones you cannot.