Okay, I'll contribute. We moved to the Bay Area (not SF, but still extremely expensive) from Texas three years ago, and I have to say that our life is a lot more Mustachian than it was there.
How do we afford it? We got lucky. Both of our jobs wanted to relocate us at the same time, so while we didn't really get a cost of living adjustment (we did get a little, but it only covered the fact that CA has income tax and TX doesn't), we found we are able to afford to live here on our salaries. Yeah, our lifestyle took a big hit, but in reality it just changed from having a lot of extra luxuries to truly enjoying life, community and friends.
So yeah, a lot of it is just luck. I think a lot of people who were raised around here just figure out a way to make it work. A lot of them live at home a lot longer or work their way up from a starter condo/FHA loan to larger and nicer houses. Keep in mind also that salaries, while still not enough to support a lifestyle like you'll get in Portland or Austin, are quite a bit higher.