I don't know what Intellij's AI integration is like, but my brief Claude Code experience is that it really chews through tokens. I think it's a combination of putting a lot of background info into the context, along with a lot of "planning" sort of queries that are fairly invisible to the end user but help with building that background for the ultimate query.

Aider felt similar when I tried it in architect mode; my prompt would be very short and then I'd chew through thousands of tokens while it planned and thought and found relevant code snippets and etc.