Atherton is the most expensive real estate ZIP code in the entire United States. The average home price is up close to 40 percent year over year, according data compiled by several Silicon Valley real estate agencies.

Real estate brokers say last year there was a frenzy of buying for homes in the $5 million range, but this year demand is shifting to the even more expensive houses. Just in the first quarter of 2014, there were seven sales of mansions in Atherton in excess of $10 million.

"We have a market here with high demand, low supply. And of course we are the center of technology. The tech sector is doing well. Everything that drives the tech sector, the local economy, venture capital, private equity. We're just the center of innovation here. So that, more than anything, drives our housing market," said Tom LeMieux of Pacific Union International, a real estate firm.

As someone who lives two towns away I can confirm the real estate market here is insane.