Set a per-call price from your cost and target margin.
If a few endpoints cost far more to serve, a flat rate lets heavy users erode your margin. Meter usage and set overage rates. Model your own upstream spend first on the API request cost calculator.
Free API monetization calculator — your cost per call and target margin to the price to charge and the profit it earns.
Start from your true cost per call (compute, upstream APIs, support), then divide by one minus your target margin. For 80% margin, price at five times cost. Add tiered plans and overage rates so heavy users pay proportionally.
Flat monthly tiers are simple but bleed margin on heavy users; pure usage-based scales with cost but is harder to forecast for buyers. Most successful APIs combine a tier (with an included quota) plus per-call overage above it.