Why gross margin sets how fast a company can afford to grow

What gross margin actually limits

Gross margin is gross profit divided by revenue. Everything else a company does has to be paid from it: sales and marketing, research and development, general and administrative costs and, last, operating income.

That makes it a ceiling on acquisition spending. If a customer generates $1,000 of revenue a year, a business keeping 10% has $100 a year to work with. A business keeping 78% has $780. The first must find a customer far more cheaply, or keep that customer far longer, to reach the same return.

The figures below are the companies' own reported numbers. Definitions differ slightly: Costco and Walmart report their rates on net sales, which exclude membership income, while Salesforce reports on total revenue.

Three margins, three different businesses

Costco's fiscal 2025 (ended Aug. 31, 2025) 10-K reports net sales of $269,912 million and a gross margin of $30,026 million. That is 11.12% of net sales. Selling, general and administrative expenses took 9.25% of net sales, or $24,966 million.

Walmart's fiscal 2026 (ended Jan. 31, 2026) 10-K reports net sales of $706,413 million and a gross profit rate of 24.2%. Operating, selling, general and administrative expenses were 20.9% of net sales.

Salesforce's fiscal 2026 (ended Jan. 31, 2026) 10-K reports total revenues of $41,525 million and gross profit of $32,255 million. That is about 77.7%, from total cost of revenues of $9,270 million.

The spread between Costco and the software company is roughly seven to one at the gross line. Costco and Walmart sell goods they must buy first. Salesforce's largest cost-of-revenue line, subscription and support, is $6,796 million.

What is left after running the business

Gross margin is only the first cut. The next question is how much of it the operating costs absorb.

At Walmart, a 24.2% gross profit rate less 20.9% in operating expenses leaves 3.3 points of net sales. Reported operating income was $29,825 million, about 4.2% of net sales. The difference comes from membership and other income that sits outside net sales.

At Costco, the arithmetic is starker. Gross margin of $30,026 million less SG&A of $24,966 million leaves $5,060 million. Membership fees of $5,323 million bring operating income to $10,383 million. Membership fees therefore account for a little over half of the operating income.

At Salesforce, sales and marketing cost $14,345 million, or about 34.5% of revenue. Research and development cost $5,993 million and general and administrative $3,000 million. Income from operations was $8,331 million, about 20.1% of revenue.

The same customer at different margins

A hypothetical example with invented round numbers shows the mechanism. Assume a customer who spends $1,000 a year and costs $500 to acquire.

At Costco's 11.12% margin, the customer leaves about $111 of gross profit a year. Recovering $500 takes more than four years, before any operating cost is counted.

At Walmart's 24.2%, the customer leaves $242 and the payback is just over two years.

At Salesforce's 77.7%, the customer leaves $777 and the payback is under eight months. The same $500 either strains the plan or barely registers.

Put the other way, the most that can be spent to win a customer is limited by gross profit per year multiplied by the years the customer stays. A low-margin company has a smaller budget per year, so it needs longer retention to spend the same amount.

A budget set against revenue overstates what the business can afford.

How low-margin companies grow anyway

Costco's filing shows one route. Its margin is thin, and its membership fee revenue ($5,323 million) is a separate line, driven by new member sign-ups and membership fee increases.

Walmart's route is scale. A 24.2% gross profit rate on $706 billion of net sales is about $171.0 billion of gross profit. The small percentage left after expenses is still $29.8 billion in operating income.

The figures above do not isolate customer acquisition spending, so the comparison here is of margins and cost structure, not of marketing efficiency.

What it changes in a growth plan

The first check is to compute gross profit per customer, not revenue per customer, before setting an acquisition budget. A budget set against revenue overstates what the business can afford.

The second is to include every direct cost in the margin. Delivery, payment processing, support and returns can belong there, even where a public filing groups them differently.

The third is to test the plan at a lower margin. If discounts, input costs or a shift in product mix cut the margin by a few points, the payback period lengthens in proportion. At 11% a two-point drop removes close to a fifth of gross profit. At 78% the same drop removes under three percent.

Evidence is limited to large public companies here. Small businesses differ in what they count as cost of sales, and margin comparisons across industries should be treated as indicative, not as benchmarks.