You make $100k in city A and spend $40k on expenses. That leaves $60k disposable.
You are considering a job in city B with half the cost of living and the same pay.
You still make $100k but your expenses have gone from $40k to $20k. Your new disposable income is $80k.
Cost of living is half but it's not like having 100% more income, it's 33% more .
Now, SF might be a great place if you have no kids, no expenses and rent a tiny little room. But, as soon as you want to have a family and backyard, you better get out! SF and CA in general is no place to raise a family. The key in this strategy is, don't put down roots in the CA bay area.
When a round of golf at a Davis Love or Fred Couples designed course costs the same as playing at a shitty muni in L.A., it feels like my disposable income has tripled.