I agree that tokens are a really hard metric for people. I think most people are used to getting something with a certain amount of capacity per time and dealing with that. If you get a server from AWS, you're getting a certain amount of capacity per time. You still might not know what it's going to cost you to do what you want - you might need more capacity to run your website than you think. But you understand the units that are being billed to you and it can't spiral out of control (assuming you aren't using autoscaling or something).

When you get Claude Code's $20 plan, you get "around 45 messages every 5 hours". I don't really know what that means. Does that mean I get 45 total conversations? Do minor followups count against a message just as much as a long initial prompt? Likewise, I don't know how many messages I'll use in a 5 hour period. However, I do understand when I start bumping up against limits. If I'm using it and start getting limited, I understand that pretty quickly - in the same way that I might understand a processor being slower and having to wait for things.

With tokens, I might blow through a month's worth of tokens in an afternoon. On one hand, it makes more sense to be flexible for users. If I don't use tokens for the first 10 days, they aren't lost. If I don't use Claude for the first 10 days, I don't get 2,160 message credits banked up. Likewise, if I know I'm going on vacation later, I can't use my Claude messages in advance. But it's just a lot easier for humans to understand bumping up against rate limits over a more finite period of time and get an intuition for what they need to budget for.

Both prefill and decode count against Claude’s subscriptions; your conversations are N^2 in conversation length.

My mental model is they’re assigning some amount of API credits to the account and billing the same way as if you were using tokens, shutting off at an arbitrary point. The point also appears to change based on load / time of day.