That makes me genuinely curious about the internal hosted vs. self-hosted usage ratio they're seeing. I'd have guessed the bulk of the cost/volume was on hosted, but clearly that can't be the case
GitHub charges too much for hosted runners. It's pretty straightforward to switch to another runner provider at literally half the cost of GitHub.
Anecdotally I've seen it get a lot more common to use third-party managed runners (e.g. Blacksmith) for anyone that needs slightly beefier machines and/or a caching system that actually works.