Break-even signup
A break-even signup is a signup whose payments have covered what it cost the offering to bring them in. If acquiring them cost $30 in marketing spend, they've now paid $30 back. They've covered themselves, but not their share of the other signups from the same batch who never paid anything.
Definition
A signup whose accumulated revenue covers the cost the offering spent acquiring them as a signup — they have reached SAC payback.
Counterpart to a profitable customer
Profitable customer names the same idea on the customer axis: a customer whose accumulated revenue exceeds CAC, the cost of acquiring them as a customer. Break-even signup names it on the signup axis: a signup whose accumulated revenue exceeds CAS, the cost of acquiring them as a signup.
The two axes differ in denominator. CAC divides total acquisition spend by customer count, which bundles each customer's own acquisition cost with their cohort-share of acquisition spend on signups who never converted. CAS divides total acquisition spend by signup count, so each signup carries only their individual share — no cohort spillover.
Individual fair-share coverage
A break-even signup has done what every signup should do: cover what the offering paid to acquire them. They haven't yet covered the share of acquisition cost attributable to signups in their cohort who never converted. That coverage is what CAC payback requires, and what distinguishes a profitable customer from a signup who has only reached break-even.
A break-even signup is past the missed conversion population — signups who never reached CAS payback because they either didn't convert at all or converted but churned without covering their own acquisition cost.
A directional proxy for CAC payback
Break-even signup sits between first-paid conversion and CAC payback in the commercial-outcome anchoring hierarchy. First-paid conversion captures binary "did revenue start" without any sustainability filter. CAC payback captures cohort-level sustainability but resolves slowly — months to a year, by which point the early-window leverage has largely closed.
Break-even signup is the milestone in between. It's faster to measure than CAC payback because the threshold is lower (cover own cost, not cohort share) and harder to game than first-paid conversion because the customer has to stick around long enough to accumulate revenue past the acquisition spend. The tradeoff is a weaker sustainability filter: a signup can reach break-even and still not become a profitable customer.
Example
A self-serve SaaS offering pays $20 in ad spend per signup. With a 10% signup-to-customer conversion rate, CAC is $200 — each customer carries $20 of their own acquisition cost plus $180 of cohort-share from nine never-converted signups. One signup converts to a $15/month plan, then churns after two payments. Their $30 in accumulated revenue covers the $20 the offering spent acquiring them: they are a break-even signup. It does not cover the $200 their conversion implicitly carried: they are not a profitable customer.