35 year olds in the bay are making closer to $300-$500k/yr, not $150k. Probably not that many renting if they don't want to
And remember that not everyone works for one of the top companies. There are hundreds of thousands of programmers in California (not sure about the bay area, although that has to account for a lot of them), most of them are well out of their twenties, and most of them don't work for Google or Facebook or anything as prestigious or well-funded.
What gives you the impression that people are making such a small amount of money in the Bay Area?