Does cities like San Francisco not have janitors? Waiters? Food delivery drivers? Or do those jobs command a six-figure salary too? If they can live comfortably in the city on a five-figure salary, maybe the argument that "cost of living is so high in SF that you can't live without a $300,000/year salary" is just a little bit overblown?
I can not imagine what one could possibly need $300,000 per year for unless an apartment costs like $200,000 per year.