Cost to Build a House in Northern California

Why it is so expensive to build in the Bay Area? 
I see $300 - 400/sq ft on many blogs about the actual cost of building here.

It does cost more to build in this area, as well as the LA basin area, and that is due to more expensive (and bureaucratic) permitting and subcontractor labor. Subcontractors charge more because it costs more to live in these areas and people are conditioned to paying higher wages.
But, it does not cost $300-$400 per sq ft ...continued

Here’s a Modern Stucco Design House from that I estimated the cost at $135 per sq. ft.
Carl Heldmann