Hopefully you'd think they compared those costs and still found the in-house option would be cheaper in the long run. Who knows, though, or who knows how accurate their estimates were.
Once you are deeply embedded with the in-house option, you have no competition. Sometimes distinct layers bleed into each other and things get even more messy to untangle. Also, sometimes due to embarrassment alone, you continue with the in-house option.
With CSPs, at least you have four major players (AWS, GCP, Azure, Oracle Cloud, ?IBM?) competing prices downward and multiple theoretical options. Yes, you have your in-house CSP expert biasing things, but since most of the work is external, at least you dont have a heavy internal weight on a home-built choice.
IMHO, the better option would be a CSP-agnostic Kubernetes based layer. But IMHO we're not there yet.
