Anecdotally, I would never move from where I live - Atlanta - to the west coast. There is nothing appealing about the area or the cost of living vs salary. I’m not saying I wouldn’t move to another major metro area if the jobs somehow dried up here.
That limits my salary (not really the COL vs salary is very attractive to me here) except I’ve seen a few local jobs for MS pop up here and jobs at Amazon (AWS) for Solutions Architects, Professional Services, etc. that I may be interested in in a couple of years.
I could also argue that a lot of companies that think they need to hire “rockstar ninja developers” to write their yet another software as a service CRUD app are mistaken and if they had to actually worry about silly things like profits instead of being subsidized by venture capital they could find a way to either relocate to a cheaper area or allow more remote work.
While I also think companies should spread out more, the very fact that so many companies are paying the significantly inflated property and labor prices in the SF area shows the tremendous economic value in having access to that labor market.