The value of square foot comps depends a lot on location. In a subdivision where the homes are mostly the same, sq ft comps are very relevant. In an area like La Jolla, where every house is different, and there are significant differences in the desirability of particular areas, the sq ft comps become much less relevant.
Looking at SDLookup.com for La Jolla, sfr’s PPSF varies from $305 to $5995 Obviously a huge varience. I don’t know enough about other areas to pick a good example of a zipcode with most houses being similar, so perhaps someone can provide a good example from Temecula or other area.