Variable pricing is common when cost depends on tokens, compute time, data volume, messages, tool calls, or the result of the work. A service may know a rate or estimate before starting while learning the final total only after measuring consumption.
Agent payments need a safe way to authorize an uncertain charge. Options include a capped budget, prepaid balance, escrow, incremental metering, postpaid credit, or a maximum hold followed by reconciliation, each with different refund and trust requirements.
ELI5
Variable pricing means the final price depends on how much service is actually used. The customer may know the rate or maximum before work begins but not the exact total.
For example, an AI task may cost according to the number of tokens and seconds of compute it consumes. The wallet can approve a clear maximum and receive measured usage instead of paying an unlimited or unexplained amount.
