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Scale economies: Costco and Fastenal win on density, not on size

The first of Hamilton Helmer's 7 Powers, and why the company with the most sales often isn't the one with the scale advantage.

By Dan Lee · November 2026

Walmart sells about 2.4 times as much as Costco, and its Sam's Club still can't match Costco's prices profitably. Grainger sells more than twice as much as Fastenal, and earns a lower operating margin. In both cases the bigger company isn't the one with the scale advantage. The advantage is density: how much volume runs through each item, each truck route and each location.

That is the first of Hamilton Helmer's 7 Powers, and the one most often claimed by companies that don't have it.

What the Power is

A scale economy is a cost that falls as volume rises. Helmer's barrier is what happens to a smaller rival who tries to match the leader's price: it loses money on every sale until it reaches the leader's volume, and it can't reach that volume without matching the price. Rational followers learn this and stop trying.

Helmer is precise about when scale counts. Two things must both be large: the share of cost that is fixed, and the leader's volume lead over the next competitor. A big company in a business where most cost is variable has no scale Power. Neither does a company with high fixed costs but no lead.

The consumer case: Costco

Each Costco warehouse carries fewer than 4,000 items, which its 10-K calls "significantly less than other broadline retailers." A U.S. Costco brings in about $340 million a year. A Sam's Club averages about $155 million, based on Walmart's 10-K, and a BJ's about $80 million, with about 7,000 items per club (BJ's 10-K). Our rough arithmetic puts Costco's sales per item per warehouse at about seven times BJ's.

That volume per item buys at the lowest cost, ships on pallets and turns so fast that suppliers fund the inventory. At the end of fiscal 2026, Costco owed suppliers $22.6 billion against $19.3 billion of inventory.

Then comes the deliberate part. Costco gives the savings back as price. Its gross margin was 11.09% in fiscal 2015 and 11.09% in fiscal 2026. Membership fees, $5.9 billion last year with 92.3% of U.S. and Canadian members renewing, pay for the low prices. Low prices drive more volume per item, and the loop repeats. Operating income tripled over the decade, from $3.6 billion to $11.7 billion, while the margin on merchandise stayed flat.

A copier faces the barrier directly. Sam's Club earned $2.44 billion of operating income in its last fiscal year, less than its $2.53 billion of membership and other income. Its merchandise roughly breaks even.

The B2B case: Fastenal

Fastenal sells fasteners and industrial supplies. Its advantage is lower cost to serve, built on local density. About 590 company-owned heavy trucks move roughly 90% of its product from 19 distribution centers to 1,595 branches, to locations inside customers' plants, and to 136,638 vending and bin units installed at customer sites (Fastenal 10-K). Those managed-inventory programs carried 44.7% of 2025 sales. Every new device or on-site location adds a stop to a route Fastenal already runs, so the cost of serving the next customer in a territory is low.

The result shows below gross profit. Fastenal's gross margin has drifted down from about 53% in 2008 to 45% in 2025 as it moved toward large accounts, yet its operating margin held at about 20%: 20.2% on $8.2 billion of sales in 2025. Grainger, more than twice the size, earned 13.9% (Grainger 10-K), and MSC Industrial 8.0% (MSC). Product mix plays a part, so the gap is evidence of the barrier rather than proof. But a regional distributor would have to fund the trucks, hubs and installed devices before it had the volume to use them.

Where it breaks

Costco's operating margin, about 3.9%, is no higher than BJ's. The Power shows up as price and growth, not margin. About half of Costco's operating profit is membership fees, so a slip in renewals hits profit almost dollar for dollar. And online, where a pallet in a warehouse matters less, the advantage is thinner. Costco names Amazon as a significant competitor.

Fastenal's density protects margin, not volume: in 2009 its sales fell about 17.5% and earnings about 34%. Its own 10-K says the shift toward larger customers is lowering gross margin. And competitors can copy the form: Grainger runs its own vending and on-site programs. What they haven't matched is the density behind them.

What it looks like in your business

In a consumer business, scale shows up as volume per product, store density and national advertising spread over more sales. A regional chain with ten stores in one metro area can have a real scale advantage there, and none in the next state.

In a B2B or industrial business, look at fixed costs: tooling, engineering, a plant that runs better full, delivery routes that get cheaper with every stop. Fastenal shows the distributor version. A job shop where material and direct labor are 70% of cost usually has no scale advantage, however large it is.

In both, the common mistake is measuring scale against the market instead of against the next competitor, and across the company instead of by product line.

Questions to ask

• What share of our cost is fixed within a year, by product line?
• By what multiple is our volume ahead of the next competitor's in each line, not of the total market?
• If a competitor matched our price tomorrow, would it make money? For how long could it afford not to?
• How much of each cost gain do we give back as price, and is that a decision or an accident?

What to do on Monday

Pull revenue per product line, then per item within it. Find the lines where your volume per item leads the next competitor's by a wide margin, and the long tail where it doesn't. The first is where scale is real and worth defending with price. The second is where pruning may do more for your cost than any acquisition would.

Costco's and Fastenal's full cases, with the numbers and sources, are in our free download, 7 Powers in practice. Next in the series: network economies.

Common questions