I was told to assume $350/square foot for new construction here in the East Bay by a design/build firm I contacted recently. So a typical 2000 sq. ft. home is $700K just for design, construction, and permits, plus $300K for land if you can find it. So it seems more like localized inflation to me. Architects and tradespeople need to pay to live here too. Plus requirements due to seismic and fire hazards, insulation requirements, etc. add to costs. Now solar panels will be required as well.

IMO prop 13 worked out really badly but it isn't the main cause of the problem, just one more giant expense for the new homeowner on top of everything else.