It's not obfuscated. The free plan gives you a max of 5 concurrent self-hosted runners. If you need more you can upgrade your plan: https://circleci.com/pricing/#comparison-table

There simply is no free lunch, somewhere someone needs to spend effort and time on managing the orchestration layer for the runners, and there is also network traffic and storage in play that costs money. If you need a future-proof CI/CD platform, it takes some investment. I agree that the Github "pay per minute" approach doesn't feel right, most people would probably find a "pay per orchestration job" or something more acceptable.

Anyway, there are alternatives out there :)