To be a little pedantic here, the numbers quoted here are San Francisco numbers, not "Bay Area" numbers. With just a quick check, I found considerably cheaper commercial lease rates in Mountain View.
You are totally right. It was heavily focused on SF. there are great options outside of SF, but all along the Caltrain stops there is really expensive space because they are more accessible. Castro Street in MV can be very expensive. It matters a lot where the founding team lives and also where you want to recruit from and at what scale. there is a ton of talent in SV as well as East Bay to pull from. Good luck on your startup! thanks so much for your comment.