Price per million charged tokens
Each published model has a USD blended rate per one million charged tokens. The usage ledger keeps input, cached, output and reasoning fields separately when the protocol reports them; the public rate is not an official split input/output tariff.
This distinction matters: an official page may show one input rate and a much larger output rate. A blended Model.sale number must be applied to the same full workload, not compared only with the official input column.
Temporary reservation
Before dispatch, a safety amount is reserved so concurrent requests cannot overrun the wallet. When terminal usage arrives, the final charge is calculated from measured tokens and the unused reservation is released.
The reservation shown in the UI is therefore a temporary hold, not a minimum final charge. If terminal usage is missing, the request remains pending for reconciliation instead of inventing a token total.
A worked example
Suppose a job uses 100,000 input tokens and 20,000 output/reasoning tokens. At a blended rate of $0.09 per million charged tokens, the estimate is 120,000 ÷ 1,000,000 × $0.09 = $0.0108. The actual ledger follows terminal usage, which may differ from the estimate.
For an official split tariff, multiply input and output separately, then add cache writes, cache reads, tools and payment fees if the provider charges them. Use the workload calculator to keep the units consistent.
Limits are part of cost control
RPM, TPM, concurrency and spend caps protect both your balance and the service. Create separate keys when an application needs a different operating envelope.
A single-request cap prevents a mistaken output limit from reserving too much balance. A daily or monthly cap limits the effect of leaked credentials, runaway retries or an agent loop.
How to compare services
Record the exact model ID, token mix, cache policy, retry behavior, payment fee and check date. Then compare the resulting total together with availability and latency. Avoid universal percentage-saving claims when the billing units differ.