Things are a bit different in SF. While you have 468 stations, we have 44. Expansion of our public transportation system has been hampered by NIMBY homeowners who have done all they can to prevent it. Rents in areas that surround BART stations (http://www.bart.gov/stations/)are still quite high, except around some of the further out stops (http://rentheatmap.com/sanfrancisco.html). Unfortunately, the further you live from the city, the more it costs to commute to the city (http://www.bart.gov/tickets/calculator/).
So while everyone moving away from the city like folks in Manhattan do would be nice, it's not that easy here.
(Aside: I miss New York public transportation.)