Now supposing your CoL is halved, your CoL needs to have been $150k+ for this to be worth it. Since you lose $75k in pay, and need to make that up from the CoL difference. If you're single, chances are you weren't spending that much on food and housing, so you actually end up with less money. But if you're supporting a big family, you may well have been spending most of your money on necessities and the CoL reduction is worth it. (At least financially.)
However, one important factor is owning a home. Housing in the Bay Area is really expensive, and substandard. Therefore, you are paying out the nose for a substandard product, and will likely never own a place, even with FAANG comp. Contrast this with most other places, where you could own a (much nicer, larger, recently built) place for the same or slightly larger expense. The high house prices also cost pretty much the same or more in property taxes, even compared to low COL areas that typically have higher property tax rates.
This one is difficult to price, because you are raising your living standard by raising your housing standard for almost the same or substantially lower housing expense (it's even better if you rent and save up even more to buy a lower-priced home in the LCOL area).
Anywhere in the US is very good compensation. London is a different story.
