The MoatWide moat

Costco Wholesale (COST) — moat facet

Half the profit is a subscription and the other half is a gross margin nobody else can survive, and neither half works without the other.

Four things protect Costco, and only one of them is the thing people usually name. The famous one — buying power — is real and is also the most copyable. Walmart buys more than Costco does. What Walmart cannot copy is the arrangement that makes Costco willing to hand the buying power straight to the customer.

Where the FY2025 operating profit came from ($M)$5,060MMerchandise$5,323MMembership fees$10,383MOperating incomeNet sales less merchandise costs less SG&A = $5,060M; dues add $5,323M.
The whole company in three bars. Selling $269.9bn of goods produced $5,060M; collecting $65 a year produced $5,323M. Each half is what makes the other possible.

Start there, because it is the load-bearing wall. Costco's gross margin was 11.12% in fiscal 20251. A conventional retailer cannot run at that number, because a conventional retailer has to cover its operating costs out of the spread between what it pays and what it charges. Costco does not have to. It covers 51% of its operating profit with an annual fee, which frees it to price merchandise at a level that would bankrupt a competitor attempting the same thing without the fee — and the low prices are what make the fee renew at 92.3%2. Each half needs the other. Neither works alone, which is precisely why the model has been imitated for four decades and matched by nobody.

The second wall is the discipline that keeps the margin where it is. Fewer than 4,000 stock keeping units per warehouse against forty or fifty thousand at a broadline retailer is not a limitation Costco tolerates; it is the mechanism. One item per category, bought in volume no supplier can ignore, sold on a pallet nobody has to unpack. It also produces the negotiating position: a brand that loses the Costco slot loses hundreds of millions of dollars of volume at a stroke, and the alternative sitting beside it is Kirkland Signature, roughly a third of company sales and the largest private label in the world3.

The third is the physical cost base, and it is quieter than the other two. Costco owns the land and building at 725 warehouses and the building alone at 141 more4, so most of its rent is a sunk cost rather than an annual escalator. It cross-docks through depots rather than warehousing, turning inventory about thirteen times a year5. And it is paid before it pays: accounts payable of $19,783 million exceeded merchandise inventories of $18,116 million at the end of fiscal 20256, so the suppliers finance the entire stock and then some. That is a float, and it costs nothing.

The fourth is the softest and the most easily lost: frequency. A membership renews because it gets used, and Costco spends real money buying reasons to visit — 747 gas stations selling fuel at about 10% of total net sales and very little margin, a pharmacy, an optician, a hearing-aid counter, a food court whose prices are a standing advertisement. This facet is rated below the other three because none of it is defensible on its own, and because it is the one showing strain: shopping frequency contributed 5 points of comparable-sales growth in fiscal 2025 and 2 points in the third quarter of fiscal 20267.

The honest limit on all four is that the moat is wide rather than deep in the way a technology moat is deep. Nothing here is protected by a patent, a licence or a standard. Anybody could open a warehouse, charge $65, cap the markup and pay well. The barrier is that doing so requires accepting three percent net margins for twenty years while somebody else already has the volume — and the one large company that genuinely tried, Sam's Club, spent fiscal 2026 with operating expenses larger than its gross profit8. It is a moat made of a decision nobody else's shareholders will let them make.

Grade all four on return on invested capital: 30.9% in fiscal 2025 against a cost of capital nearer 7%9, up from 18.6% a decade earlier. A retailer earning four times its cost of capital on owned real estate and negative working capital is not being flattered by leverage or accounting. If the moat is real, that spread holds while the fee goes up; if it is not, the spread narrows first.

Moat trajectory: Holding steady

Return on invested capital has climbed from 18.6% to 30.9% over a decade, but every component of the moat is mature rather than compounding. This is a fortress being maintained, not extended.

The number that tests this moat
Moat Explorer calc
Return on invested capital vs an assumed ~7% hurdle
30.9% in fiscal 2025, from 18.6% in 2016

A retailer earning four times its cost of capital on owned real estate and negative working capital is not being flattered by leverage. If the moat is real the spread holds while the fee rises; if not, it narrows first.

How it's calculated: NOPAT (operating income x (1 - effective tax rate)) divided by average operating invested capital (total assets less current liabilities less cash), computed from Costco's SEC XBRL filings by tools_roic_edgar.py. The ~7% hurdle is an assumed WACC, not a filed figure.
Source: Costco Form 10-K, fiscal year ended August 31, 2025 ↗
Aspects of the moat
DIG DEEPER 01
The Dues Are the Profit
A $65 fee with no cost of goods, collected a year in advance, out-earns everything sold inside 914 warehouses.
DIG DEEPER 02
Eleven Percent, By Rule
The gross margin is not what Costco can get; it is what Costco allows itself, and the discipline is the asset.
DIG DEEPER 03
The Cost Position
Owning 866 buildings, turning stock thirteen times a year and being paid before it pays is what makes nine percent of sales enough to run on.
DIG DEEPER 04
The Reason to Come Back
A membership renews because it gets used, so Costco spends real money — fuel at no margin, a $1.50 hot dog — buying visits.
References
  1. ReportedCostco's gross margin was 11.12% in fiscal 2025.
    Costco Form 10-K, fiscal year ended August 31, 2025 - Item 7 MD&A (net sales $269,912M, membership fees $5,323M, gross margin 11.12%, SG&A 9.25%, comparable-sales composition, capital expenditure, dividends and repurchases) — FY2025 · publ. October 8, 2025 · source ↗
  2. ReportedIt covers 51% of its operating profit with an annual fee, which frees it to price merchandise at a level that would bankrupt a competitor attempting the same thing without the fee — and the low prices are what make the fee renew at 92.3%.
    Costco Form 10-K, fiscal year ended August 31, 2025 - Item 1 Business (membership counts and renewal rates, warehouse and gas-station counts, under 4,000 SKUs, Executive tier and the 2% reward, human capital and wages, competition, Kirkland Signature) — FY2025 · publ. October 8, 2025 · source ↗
  3. ReportedIt also produces the negotiating position: a brand that loses the Costco slot loses hundreds of millions of dollars of volume at a stroke, and the alternative sitting beside it is Kirkland Signature, roughly a third of company sales and...
    Costco Form 10-K, fiscal year ended August 31, 2025 - Item 1 Business (membership counts and renewal rates, warehouse and gas-station counts, under 4,000 SKUs, Executive tier and the 2% reward, human capital and wages, competition, Kirkland Signature) — FY2025 · publ. October 8, 2025 · source ↗
  4. ReportedCostco owns the land and building at 725 warehouses and the building alone at 141 more, so most of its rent is a sunk cost rather than an annual escalator.
    Costco Form 10-K, fiscal year ended August 31, 2025 - Item 2 Properties (725 warehouses with owned land and building, 141 land-only leases, 134.7 million square feet of selling floor and 32.2 million of distribution) — FY2025 · publ. October 8, 2025 · source ↗
  5. Moat Explorer calcIt cross-docks through depots rather than warehousing, turning inventory about thirteen times a year.
    Moat Explorer calculation: FY2025 merchandise costs of $239,886M over average merchandise inventories of about $18,382M gives roughly 13 inventory turns (about 28 days); accounts payable of $22,363M over inventories of $19,418M gives 115% at Q3 FY2026 — FY2025 and Q3 FY2026 · publ. September 2026 · source ↗
  6. ReportedAnd it is paid before it pays: accounts payable of $19,783 million exceeded merchandise inventories of $18,116 million at the end of fiscal 2025, so the suppliers finance the entire stock and then some.
    Costco Form 10-K, fiscal year ended August 31, 2025 - consolidated financial statements and notes (income statement, balance sheet, Note 11 segment reporting, disaggregated revenue by merchandise category, legal proceedings) — FY2025 · publ. October 8, 2025 · source ↗
  7. ReportedThis facet is rated below the other three because none of it is defensible on its own, and because it is the one showing strain: shopping frequency contributed 5 points of comparable-sales growth in fiscal 2025 and 2 points in the third...
    Costco Form 10-Q, quarter ended May 10, 2026 - MD&A (comparable sales +10% and +7% excluding fuel and currency, ticket +7% against frequency +2%, membership fees $1,373M, renewal 92.2% and 89.7%, gross margin 11.04%) — Q3 FY2026 and the first 36 weeks · publ. June 3, 2026 · source ↗
  8. ReportedThe barrier is that doing so requires accepting three percent net margins for twenty years while somebody else already has the volume — and the one large company that genuinely tried, Sam's Club, spent fiscal 2026 with operating expenses...
    Walmart Form 10-K, fiscal year ended January 31, 2026 - Sam's Club U.S. segment (net sales $93,015M from 601 clubs and 81 million square feet, gross profit $10,556M, operating expenses $10,639M, membership and other income $2,525M, operating income $2,442M) — FY2026 (ended January 31, 2026) · publ. March 13, 2026 · source ↗
  9. Moat Explorer calcGrade all four on return on invested capital: 30.9% in fiscal 2025 against a cost of capital nearer 7%, up from 18.6% a decade earlier.
    Moat Explorer calculation from Costco's SEC XBRL filings (tools_roic_edgar.py): NOPAT divided by average operating invested capital, 18.6% in FY2016 rising to 30.9% in FY2025 — FY2016-FY2025 · publ. September 2026 · source ↗
Sources
Generated September 23, 2026