$300k for new construction is ludicrously cheap for most coastal California cities. I was told to budget $150-250k for permits when I considered buying land and building my own house in Santa Barbara.
Both my current and my previous house would be illegal to build today because they are too large (even though both houses comfortably fit the frontage requirements, there is an additional X square feet of livable space per Y square feet of lot; in all R-1 zones, the calculation is such that a single-story house can usually hit the dwelling-space limit, so most 2 story houses in town would be illegal to build today).
Santa Barbara is significantly cheaper than bay area in terms of renting or buying real estate.
The 2br apartment I'm currently renting in SB is $2.6k/mo. A very similar apartment in Redwood City is over $4k/mo.