...but here in the Pittsburgh PA area, the suburbs are only a few miles from Downtown. We do have upper middle-class areas within the city, but the vast majority of the population would rather live in a suburb to avoid the crowds and crime that bleeds out of the poor areas and their associated gang issues. My house is 15 miles from downtown, across the street from a golf course, costs me 775/mo in rent. You can't rent a shoebox in SF for that much.
Really, tech is going to move away from areas like Silicon Valley, the Bay area, etc. in favor of smaller cities across the country. Collaberation via the Internet makes it possible to group smart people regardless of geography - and cost of living DOES matter. Especially once you go past 30 years old and care less about the club scene and more about what you get for your money. And it is a good deal for employers to hire someone at 60k in Pittsburgh that they would have to pay 120k in CA - and the employee can have a higher standard of living too.