Fundamentals are what set the price floor of an asset in the absence of speculation.
For real-estate in most areas that would be income. As we are seeing in parts of Detroit, local unemployment can drive the retail value of many properties to effectively zero.
In San Diego, as we are a big tourism destination, there is also a market for second vacation homes here. This will prop up the median housing cost somewhat above what one would expect vs. the median income.
*However*, this will only drive up demand for homes that rich folk are going to want to vacation in. Properties in the ghetto and IE need not apply.