This is about how much money I made when I lived in San Francisco for a few years mid-decade.

It was doable primarily because I always lived with people who had rent controlled apartments or houses they'd lived in for some time. The cheapest rent I paid--and where I lived longest--was $550/mo. My girlfriend lived with me there and we split it 50/50.

Other things contributing to low living expenses: no car (huge savings); no TV; aggressive (but perfectly legal) tax deductions; choosing fun activities over costly purchases; freegan friends who gave us loads of food; and, of course, two buck chuck...

It's certainly doable.