It's why every integration basically tries to piggyback off of a subscription, and why Anthropic has to continuously play whack-a-mole trying to shut those services down.

Monopoly isn't the only thing that allows you to charge large margins.

API inference access is naturally a lot more costly to provide compared to Chat UI and Claude Code, as there is a lot more load to handle with less latency. In the products they can just smooth over load curves by handling some of the requests slower (which the majority of users in a background Code session won't even notice).