"AWS is overpriced service for people that do not have time or resources to do things on their own and pay massive prices for that."

Isn't that the point of AWS?

The time / resources cost to build (monitor and maintain..) your own infrastructure isn't zero.

Did these companies have spare teams lying around the place, such that no new hires were needed to make the transition? If not, then it's not so much of a saving at the current cost of dev / ops personnel, just now on a different balance sheet.