Costco Doesn't Make Money Selling You Things. It Makes Money Letting You In.

Ask most people how Costco makes money and they'll say: it sells in bulk, cheaply, to lots of people. Reasonable — and wrong in the way that matters. Costco's retail operation, the mountains of paper towels and the rotisserie chickens and the absurd vats of mayonnaise, runs at a profit margin so thin it barely registers after you subtract the cost of operating the warehouses. The company earns a large share of its operating profit somewhere most shoppers never think about: the annual membership fee you pay simply to walk through the door. And the loyalty that makes this work is measurable: Costco's member renewal rate was 92.7% in the U.S. and Canada and 90.4% worldwide at the end of fiscal 2023.¹ Once you see it, you can't unsee it. Costco isn't a retailer that happens to charge a membership. It's a membership club that happens to run a near-break-even buying service for its members — and the entire machine is built around that inversion.

The mechanism: why thin margins are the strategy, not a sacrifice

The crucial thing to understand is the direction of causation, because it's the opposite of what intuition suggests. A normal retailer keeps prices as low as competition forces it to, and profits on the margin it can preserve. Costco does the reverse: because the membership fee carries the profit, the company has every incentive to push merchandise prices as low as humanly possible. Low prices aren't a cost that eats into Costco's profit — low prices are the product the membership buys. The cheaper the goods, the more obviously worth-it the card; the more worth-it the card, the higher the renewal rate; the higher the renewal rate, the bigger and more predictable the fee income. The flywheel runs on its own thinness. This is why Costco famously caps the markup on most items at a low ceiling, and its Kirkland house brand only a hair higher. To a normal retailer that cap is a handcuff. To Costco it's the engine: the cap guarantees members a deal they genuinely can't find elsewhere, which protects the renewal rate, which protects the profit.

The $1.50 hot dog, decoded

Now the famous hot dog. Costco has held its hot-dog-and-soda combo at $1.50 since the mid-1980s³, reportedly losing money on it, reportedly under a standing internal order never to raise the price. To an accountant, this is indefensible. To the money machine, it's marketing genius costing pennies. The hot dog is a loss leader in service of the real product — the membership. It says, loudly and deliciously and at the exact moment a member is deciding whether this place is worth it, that this is a company that is absurdly, almost irrationally, on your side. That feeling is precisely what renews the card. And because the dollar has lost well over half its purchasing power since the 1980s, Costco hasn't merely frozen the price — it has quietly made the hot dog cheaper in real terms every single year, deepening the signal at no incremental strategic cost.

Why almost no one can copy it

Plenty of retailers have tried to bolt a membership fee onto a normal markup, and it rarely works — which tells you the fee isn't the trick. The trick is the discipline behind it. A membership fee only holds if the member is genuinely, provably better off paying it, and that requires the institutional willpower to leave money on the table at the register every single day, forever, while public-market pressure screams at you to fatten margins by a point or two. Most companies can't withstand that pressure; the quarter always wins. Costco's true moat isn't the warehouse or the bulk buying or even the Kirkland brand — it's the organizational restraint to keep retail margins thin when every short-term instinct demands otherwise. That restraint is cultural, it's decades deep, and it cannot be acquired in a strategy offsite, which is exactly why competitors who copy the format rarely copy the result.

It's worth being honest that this model is non-transferable, because that's the real lesson. You can't paste the 'Costco playbook' onto a company whose customers won't pre-pay for the privilege of buying, or whose leadership can't stomach near-zero retail margin. Every visible piece — the markup cap, the few-thousand-SKU count, the treasure-hunt layout, the hot dog, the famously high wages that keep stores staffed and turnover low — exists to defend one number: the renewal rate. Pull any single element out and stand it up elsewhere, and it collapses, because the parts only work as a system pointed at that one metric.

The high wages deserve a closer look, because they're the piece that most often gets dismissed as Costco being 'nice,' when they're actually load-bearing. Paying warehouse staff well above retail norms drives down turnover, and low turnover is an efficiency engine: experienced employees move more volume per hour, make fewer costly errors, and need less re-hiring and re-training. That operational efficiency is what makes razor-thin retail margins survivable in the first place — a sloppier, higher-turnover operation simply couldn't run at Costco's markups without losing money. So the generous pay isn't charity competing against the thin margins; it's the thing that makes the thin margins possible, which makes the deal credible, which protects the renewal rate. Even Costco's reputation as a good employer feeds the machine: it's part of the same 'this company is on your side' signal the hot dog broadcasts, aimed at members and workers alike. Once you see the system this way, the apparent contradictions — generous wages, punishing margins, an unprofitable hot dog — resolve into a single coherent strategy where each 'soft' choice is doing hard financial work.

So the next time you walk out of a Costco with $300 of things you never planned to buy, remember that the company barely made a cent on any of it. It already made its money the day you renewed the card — and everything inside, right down to the gloriously underpriced hot dog, exists for one purpose: to make sure you do it again next year.