A cost model, price hypothesis and payment-evidence plan.
2026-10-26.2 · 40 minutes estimated; work in several sessions
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Prerequisites and goal
Define a charging unit such as a task or monthly subscription.
Start with diagnostics; skip explanations you can already apply independently.
Define the unit and cost boundary
Price minus variable cost is contribution before fixed costs. Include inference, human review, payments and retries; model low, medium and high use. Revenue, profit and cash timing differ. Free credits are not a permanent cost basis.
Test price with behavior
Stated willingness is a starting point, not a sale. Record real offers, informed trial terms and purchase or refusal reasons; disclose deliverable limits. Avoid confident lifetime-value estimates from unstable retention. Report observed contribution by period and incurred acquisition cost.
Worked example · fictional
From a problem to inspectable work
Fictional teaching model: monthly price 50, variable cost 20 and fixed cost 600, excluding tax and other costs.
Contribution is 30 and break-even 20 units; at cost 35, contribution is 15 and break-even 40.
A real model must add churn, refunds, labor and cash timing.
Show normal and high-use scenarios with cost boundaries; next verify actual usage and payment behavior.