Given the fact that you are discussing prices in 1991 which was the end of the last bubble, I would say that the fact that Carmel Valley was affordable back then was because it was considered an outlying area of San Diego and obviously had lots of open land available for building. Back in 1991 Qualcomm was a startup and had well under 1000 employees as well so obviously the demand for areas near Sorrento Valley was insignificant compared to what it is now.
Your example illustrates nothing more than the basic concept of supply and demand. The demand for that area has obviously increased exponentially over the last 20 years and you see the result in the prices.
By contrast some areas like Mt. Helix that were actually very popular in the 1980’s are actually just about the same price now as they were then so you could say on a relative basis demand in that area has been flat if not actually shrinking over the last 20 years.
The demand in San Diego County has clearly shifted into North County and I expect that the big reason for that is newness of the housing stock, superior schools, and closer proximity to the major new employment areas.
