This is how Firebase, Supabase and friends work.
Getting 100 people to sign up for a free service is still work, but significantly less.
If not, then you are in the ad business.
I suspect there's a special dynamic for developers. I'm usually more willing to try out new things on personal projects, but I also don't like paying for things on personal projects. At work I don't care how much things cost, but I'll definitely advocate for tools that worked well on personal projects.