Public transportation needs to be fixed first so that people from east bay and beyond can get to the Silicon Valley and SF faster.
If I could live in Tracy and get to SF in 30 mins or even 45 mins, I would move there in a heartbeat. But it takes 1.5-2hrs even with BART.
That will do more to lower house prices than cramming a small number of houses or condos in an already crowded area.