The answer can be found by looking at how most of the commercial open source products are monetized. Software hosting and technical support are quite lucrative if the software is valuable.

This only applies to some software, though, no? Like, let's say a group of folks make a game or something, and release it as FOSS. Assuming they're not hobbyists, and this is their career, how are they covering costs and making a living on that?

How do content creators get paid?

Largely through sponsorships, I think, right? Sponsorships and crowdfunding, but both of those require some measure of notoriety. It's an unfortunate case where you have to spend a lot of effort doing it effectively unpaid until you get a following large enough to bring in sponsorship money or ad revenue or donations. Or you need to be a pretty woman who's willing to monetize that, that seems to have a much lower barrier to entry.