That is because LLM KV caching is not like caches you are used to (see my other comments, but it's 10s of GB per request and involves internal LLM state that must live on or be moved onto a GPU and much of the cost is in moving all that data around). It cannot be made transparent for the user because the bandwidth costs are too large a fraction of unit economics for Anthropic to absorb, so they have to be surfaced to the user in pricing and usage limits. The alternative is a situation where users whose clients use the cache efficiently end up dramatically subsidizing users who use it inefficiently, and I don't think that's a good solution at all. I'd much rather this be surfaced to users as it is with all commercial LLM apis.