You wouldn’t be charged thousands because the service is pre-paid. Your websites will be suspended once the balance runs out, but you can re-establish them once you add more balance.
AFAIK is the only provider in which you can have functional billing limits and not just alerts that still depend on you reacting on them in time.
Where in the terms of service or in the admin UI do you see this information? You can pre-pay, yes, and the CDN service (and ONLY the CDN service) has a setting to stop the billing. But the other services do not seem to have a limit on how much you can get billed.
Problem is, Cloudflare's free tier plan effectively sets the limit to $0.
Exactly!
I once had some pretty serious DoS attack, but fortunately, I didn't had to pay more than what was pre-paid.
It's not purely prepaid otherwise I wouldn't be charged into negative (see my other comment in this thread).