You'll still need to retire in a cheap city in Nowhereville. Why not live in SV when you're young and retire to Nowhereville, vs living in Nowhereville all your life?
Alternatively, if you can get a remote job, live in Cambodia or the Phillipines or somewhere else with an extremely low cost of living while getting paid 0.5x SV salary, and end up with 95% savings. Then you can retire anywhere.
0.5 salary (generous for someone remote working in a different timezone without a large personal network, imho) with 95% savings is the same as 48% savings with 1x salary, not to mention greater growth potential. You're example doesn't seem all that different from working in the valley a few years, then cashing out to retire in SE Asia.
>Why not live in SV when you're young and retire to Nowhereville, vs living in Nowhereville all your life?
Depends on your preferences. I don't want to move to a new place when I retire. I'd like to retire in the same place where I have friends, know the city, system, etc.