Waking up to a 10k vercel bill is pretty common, especially when a DDoS goes undetected. That 10k bill is roughly $50 dedi from hetzner, but the problem with that is that you need a distributed system, for that you need something more advanced that tau, let's say kubernetes, then you need multi-site storage ok so ceph and then you realize you need a degree in openssh and bluestack to continue on and realize that the hassle from all of that and instead just hire a sysops employee that costs 10k a month and spend $1000+/month on hardware for geo-distribution.
Take this from personal experience. I've personally seen someone go k8s with very little experience and their general consensus was that they just want to go "managed" hosting instead.
Still better than 10k bill once your app becomes large enough, but it's simply not something devs that just want to get something out there want to bother with. In the end even with the insane hosting costs compared to the revenue they bring in is tiny. $10/month service user only racks in around $1 of api usage a month, heavily depends on the app though.