Median sales prices can rise because of increases in fair market value – i.e. buyers are paying more money for the same home (supply and demand) – and/or because buyers are purchasing larger, more expensive houses, often in more expensive communities. Both dynamics are currently at play, but it is certain that affluent and very affluent buyers have made up a dramatically increasing percentage of the demand in Marin and Bay Area markets.
This next chart illustrates the large year-over-year increase in the average size of houses sold.