I don't want to make my assumptions how it is charged, or run a rather costly experiment of switching to API usage.

I use ccusage, and it already covers a very different pricing for cached input. I asked Opus 5 to cross-check that and claims it is fine.

Since you want data (it is for the last 30 days):

  output:         $684 (12.5%)
  cache reads:  $3,311 (60.4%)
  cache writes: $1,483 (27.0%)
  fresh input:      $6 ( 0.1%)

thank you very much for the input. I once said to my friend that "no actually you do not get $20k worth of API usage for $200 subscription, it is mostly $600". turn out it was a pretty close guess.

even if anthropic does not apply all the fancy techniques that deepseek is using for their cache system, tiered kv cache system is something that anyone implements. the US labs even have huge CXL memory pool system. basically they charge us premium for what is almost free. no wonder they are pretty generous with the quota.

inb4 "but you will have to use api if not for the sub", no it is the other way around: because you have the subscriptions so people rarely have to pay for that input cache markup. if they have to pay that much money they would just simply switch models.