Prompt Caching Costs: Cache Writes, Cache Hits, and Break-Even Math

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Prompt caching can reduce the cost of repeated input. The saving depends on how much input is eligible, how often it is reused and how the provider prices cache writes and reads.

A 90% discount on cached input is not a 90% discount on the whole request. Output tokens, uncached input and any other charges still count.

Two different kinds of caching

reuses processing for eligible repeated input while the model generates a new response. returns a previously stored answer under a matching policy. They have different behavior and should not share one undifferentiated savings claim.