Day 183: When Paying More to Cache Costs Less
A cheaper cache read does not make the first request cheaper. Someone has to pay to write the cache before a later request can reuse it.
For a founder budgeting an agent-assisted commercial workflow, that distinction changes the retention decision. Substantial instructions or reference material might repeat across requests, but the interval between those requests determines whether paying extra to retain them makes economic sense.
Here is a worked cost model for Zero-Shot Agency, using Claude's published prompt-caching rules. It is arithmetic, not an API experiment, customer traffic trace or claim of savings we have delivered.