Metrics
Payback period
Months until cumulative gross profit per customer recovers CAC.
Payback is the time it takes to recoup acquisition cost from a customer's gross profit. SaaS norm is 12–18 months. E-com DTC norm is 0–3 months (most try to be first-purchase profitable). Long-payback businesses need patient capital and tight cohort tracking; short-payback businesses have flexibility but rarely scale beyond their organic ceiling.
Example
Subscription supplement brand: $58 CAC, $19/month gross profit per active subscriber, 71% month-2 retention. Payback ≈ 4 months. Quarterly cohorts confirm.