If you look at the actual cost of your Claude Code conversations, you'll see that the cost is overwhelmingly dominated by the cost of input tokens (cached). Because of how we construct persistent conversations, each cached input token incurs cost on each API request, meaning that component of cost scales with O(request count). If you graph the cost curve of a claude code session, it's very obvious that this scaling factor overwhelms the cache discount.

Here is a blog post that shows some data - https://blog.exe.dev/expensively-quadratic. And I can confirm this is true for Claude Code - I set up a MITM capture for all Claude Code requests and graphed it.

So increasing Request Count that reuses the same prefix (which is what higher compaction thresholds do) really does lead to (substantially) higher API costs.