Well funny because the San Diego listing you showed is the home I listed for a client a few months ago. His parents passed away and they sold it. The reality is that the neighborhood is a mid 200k hood for homes but the flippers have come in, swamped it, and are now making good bucks on flips. It would not be considered a nice neighborhood with decent school districts by any means.
I do understand your point from a numerical standpoint. I think that the quantity of sub 400k homes in San Diego is higher simply because of a mix of lower income spread between the middle of the county. Additionally out to the east and northeast there are plenty of lower priced options.
Still the stress for the neighbourhoods that most residents want to be in and/or desired school districts can be classified as historically high.