Best way I can think of:

http://www.zillow.com/HomeDetails.htm?zprop=69021732 (a similar house in 4S ranch)

“This home at $750,500 is valued higher than 80% of homes in San Diego County”

http://factfinder.census.gov

582,885 1-unit, detached housing units

So there are 116K houses in the county more expensive than this one. (Ignore mello-roos for a moment)

Some wealthy families will be renting and some expensive houses will be occupied by low-income retirees, so we can pretend that these effects cancel each other.

As of 2006, 116K’th wealthiest family made around 140K/year.

Per 28% rule, in theory, at 140K/year you can afford to pay $3300/month for housing.

(Quick craigslist search finds a smaller house offered at $2995, and a bigger house offered at $3700, so I seem to be right on target)

This house price will be in line with rent if you can get it for $3300/month.