Some of the building codes are probably overkill, but part of the difference in California building costs compared to other states are energy efficiency requirements (like more expensive windows) that quickly pay for themselves in reduced costs to live in the unit and also reduce per capita energy usage. Unfortunately, neither the developer or landlord (if the unit is built for a rental) has incentive to build an energy efficient building as the tenant is going to eventually pay the energy costs. These requirements absolutely need government regulation because the "free market" leads to a non optimal outcome.