> Probably because actual time required to manage a db server is really unpredictable.
This, and also startups are quite heterogeneous. If you have an engineer on your team with experience in hosting their own servers (or at least a homelab-person), setting up that service with sufficient resiliency for your average startup will be done within one relaxed afternoon. If your team consists of designers and engineers who hardly ever used a command line, setting up a shaky version of the same thing will cost you days - and so will any issue that comes up.
This, and also startups are quite heterogeneous. If you have an engineer on your team with experience in hosting their own servers (or at least a homelab-person), setting up that service with sufficient resiliency for your average startup will be done within one relaxed afternoon. If your team consists of designers and engineers who hardly ever used a command line, setting up a shaky version of the same thing will cost you days - and so will any issue that comes up.