Chalk it up to the median math. The median county wide will be $250,000. That means places like La Jolla hypotethically are still $700K, Santee is $350K and National City are $150K. Keep in mind the median is a mix of condos, SFHs, townhouses including both the good and bad areas.
Santee has a 2005 median household (family) income of $73.8K