As someone currently having moved from the southwest, to bay area, to northeast, and now living in the south, you underestimate the cultural changes. I have relatively little in common with people who grew up here. They're fine people, but they're not people who I can talk to past small talk.
And in a fair number of these places, there's the same hostility to people moving in as the bay area.
The US Midwest and South have a dozen relatively cheap cities to live in where it isn’t depressed.
Housing supply/demand balance is a prime contributor to CoL, and the south/Midwest generally doesn’t have the draconian housing restrictions that the coastal cities have.