Unit economics: why growing companies lose money
The difference between a business that scales and an expensive way to buy customers.
A company losing $100 million a year can be a wonderful business or a doomed one, and the income statement alone cannot tell you which. The tool that can is unit economics: the profit or loss on a single customer, viewed over that customer's whole life.
Two numbers, one ratio
Customer acquisition cost (CAC) is total sales and marketing spend divided by new customers won. Lifetime value (LTV) is the gross profit a customer generates before leaving. The relationship between them is the verdict: pay $100 to acquire a customer worth $500 and losses are an investment — each dollar of marketing buys five. Pay $100 for a customer worth $80 and growth is a machine for destroying money, and scaling it makes things worse.
Where the self-deception hides
LTV is a forecast, and forecasts flatter. The classic errors: using revenue instead of gross profit (a $500 customer serviced at 40% margin is a $200 customer); assuming today's low churn holds for years when early adopters always churn less than the mass market; and blending paid acquisition with free word-of-mouth customers, which makes paid marketing look cheaper than it is. A rule of thumb from venture investing: treat any claimed LTV/CAC ratio above 3 with respect, and any above 5 with suspicion.
Payback period, the honest metric
The measure hardest to game is CAC payback: how many months until a customer's gross profit repays the cost of acquiring them. Under 12 months is strong; beyond 24, the company is financing a long loan to every new customer, and needs patient capital to survive its own growth.
The reading habit
When a growing, unprofitable company reports results, skip the net loss and ask three questions. Is gross margin healthy and stable? Is CAC payback shortening or stretching? Do older customer cohorts still spend, or do they leak away? Amazon lost money for years while its unit economics were excellent; plenty of delivery startups showed the opposite pattern. The losses looked identical. The businesses were not.