Comment by lich_king

Stick-frame single-family construction is pretty inexpensive. For a single-story structure, rough framing and roof can be done by a couple of low-wage laborers with simple tools in a week.

Prefabrication doesn't save all that much money: you still need several guys, now with a crane, and you need to ship and deliver an oversize load. A lot of the cost is finish (including cabinets, countertops, appliances), and in California, land and compliance.