All of the new housing in the Bay Area is at a premium price. All of it. There are tens of thousands of condos slated to be built in SF. They are all top of the end condos. They haven't and they won't dent the prices. Building more homes will just let more rich people move to the Bay Area and it will sustain prices.
Supply will increase at a much, much lower rate than demand when it comes to housing. Unless you literally create ghost cities like in China, you won't get the effect that you want.
The only way to curb prices is to reduce demand. Force Facebook, Google and Amazon to build outside of the Bay Area. I guarantee that will be the quickest way to curb demand and to throttle house prices. Have Google build in Kansas City instead of San Jose. Have Facebook build in Detroit. There's enough money to sustain an entire ecosystem and it will help increase house prices in other areas and dampen demand here.