Of course, that's not actually a bad thing if their remaining income is higher in absolute terms (or adjusted for non-rent cost of living) than it would be in o

Of course, that's not actually a bad thing if their remaining income is higher in absolute terms (or adjusted for non-rent cost of living) than it would be in other cities. The percentage income isn't really relevant on its own. I'd rather make $10m a year and spend 90% of it on rent than make $100k a year and spend 20% of it on rent. And when you add in the subjective value of living in SF (which is small or perhaps slightly negative to me, but surely large for many people), it could still be a perfectly reasonable decision to live and work in SF.