I wonder what would be the cost without k8s setup and no containers at all, pure compute nodes. I bet my last socks twice less, at least.
Let's not forget that you'd also have to pay at least 3 (8 hours per shift, not accounting for weekends) people to ensure 24/7 service availability through those 15 Hetzner nodes.
AWS/GCP/Azure et al make it so you generally don't need to worry about the infrastructure part of the problem. Everything else still applies though.
This is true if you run your own datacenter, but dedicated server providers typically monitor their servers and immediately intervene if they detect any connectivity/network issue (which is outside our control even if we use cloud providers like AWS).
For individual server failure (disk issue, etc), how you handle failure condition on dedicated servers is not much different than handling failure on cloud servers (remove the bad server from the cluster, re-image a new server and join it to the cluster). The main difference is provisioning new physical server is not instant, so you'll need to plan ahead and either have some spares or slightly over-provision your cluster (so you can take down a few nodes without degrading your service). You can do this automatically or manually, not much different than using cloud servers.
Using dedicated servers is not as scary as what people thought it would be.