Publish it. On a public page, with real numbers, before signup. I trust providers more when pricing is front and center, and so does everyone else, because hidden pricing signals that the number depends on who is asking.
Price against the value the consumer receives, not against what it costs you to serve. Your infrastructure cost is your problem; the consumer is buying an outcome. This is also why SaaS-style tiers translate badly to APIs: SaaS tiers bundle features per seat, while API consumption is a continuous volume that does not respect tier boundaries. Consumers end up on a plan that is either mostly wasted or constantly overrun.
Make the unit predictable. A consumer needs to be able to estimate their bill before they build. If your pricing requires a spreadsheet with four variables and a weighting factor, you have made evaluation expensive and people will choose the provider whose cost they can predict.
Break the page down properly — what each plan includes, per-operation costs where they differ, what happens at the limit, what overage costs. SendGrid’s transparency is the pattern worth copying.
And if you might charge later, say so now, in writing, with as much specificity as you can. Introducing pricing on an API that people built free businesses on is the single most trust-destroying move available, and the only thing that mitigates it is having told people in advance.
