It isn't just that they wanted to charge for using your own action runners. It's that the price was almost as much as using GH's hosted action runnners. Which didn't even include the cost of hosting your own runners.

I think removing the free tier altogether would be a bad move, especially given that some important open source projects rely on it. But they could possibly lower some of the limits, especially for new accounts, with a way for open source projects to apply for more, and maybe have an automatic scale up for projects that are more popular, by some metric. And maybe limit the free tier to public repos, and maybe even only repos that use an OSI approved license or something.