This is the reason I use Heroku and would never on a personal level use some of the bigger solutions, or apparently Fly.io. As an individual and despite being generally careful, I just cannot have a tiny risk of having a $100k+ accidental bill. I'd rather my project goes down if there's a DDOS attack, or if I made a typo and created an infinite loop. If I take some of my hobby projects to the "next level", it'd be def behind a LTD company.
It could also be a simple user error- there’s been stories on HN on how people racked up massive bills for example because CI was running continuously etc.