CAC and payback

The formula, in plain HTML

impressions = budget ÷ CPM x 1,000
orders = impressions x visit_rate x cvr
CAC = budget ÷ orders
payback_orders = CAC ÷ (AOV x contribution_margin)

The CPM input is the only externally sourced number Libsyn Ads · Jul 2026; everything else is your funnel. This is the exact engine inside the Test Modeler, and every playbook scenario on this site reproduces it with the division shown, so any figure can be re-derived by hand.

Payback, worked

At $80 AOV and 60% contribution margin, each order contributes $48. A $120-130 CAC therefore needs 2.5-2.7 orders per customer to pay back (120 ÷ 48 = 2.5; 130 ÷ 48 = 2.71). If your repeat-purchase curve delivers a second order from 40% of customers and a third from 20%, expected orders per customer run 1.6 and the channel does not pay back at these assumptions; at 70% and 45% it runs 2.15 and gets close. This is the conversation to have before spending, not after.

Benchmark against your blended CAC

A podcast CAC means nothing in isolation; it means something against your blended CAC and your marginal channel CAC. If blended sits at $90, a $125 measured podcast CAC is a premium you might pay for channel diversification and creative halo, or might not. Benchmarks and the blended-vs-marginal distinction: averagecac.com.

Sensitivity, honestly

The model is linear in both assumptions: halve the visit rate and CAC doubles ($240-260); halve CVR and it doubles again. Present the readout as a 2x2 (visit rate x CVR, each at half and full assumption) so the decision maker sees the failure cases priced. The high-CAC-still-acceptable argument (brand, halo, discovery) deserves exactly one sentence in a readout and zero load-bearing weight; if the model only works with unmeasured halo, the model does not work.