The Third Price: I Measured Prompt Caching Across 393 LLMs and Found a 90% Discount Hiding Behind One JSON Field

Same model. Same prompt. Ten minutes apart.

Source: [Dev.to](https://dev.to/ptokito/the-third-price-i-measured-prompt-caching-across-393-llms-and-found-a-90-discount-hiding-behind-eck)