You've heard it before: the rich are getting richer.
And that's nowhere more evident than here in Atherton, California. The private mansions—rarely seen from the road—are experiencing a pricing renaissance.
High-end homes in Atherton are selling like hotcakes, and often over the asking price, and frequently for all cash. That's saying something when you are talking about $10 million-plus estates.
Location is a big reason why Atherton is the perfect place for the super-rich. The town is 45 minutes south of San Francisco, and less than 20 minutes to the headquarters of Facebook, Google and most of the major tech companies in Silicon Valley.
In fact, 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.
There are many exclusive communities for the elite in Silicon Valley including Woodside and Los Altos Hills. But brokers say Atherton is by far the most sought-after location and buyers are moving fast.
Ken Deleon of Deleon Realty just sold a mansion in Atherton for $14 million to a Chinese buyer in 72 hours.
"One of the reasons Atherton is so hot right now is that Forbes recently named it the No. 1 most affluent ZIP code in America. A lot of my clients, particularly the Chinese, are prestige-driven. They want to be in the best area in all of America. That really helped Atherton's stock," said DeLeon.
Brokers say their buyers are all cash and that investors from China will often pay for a mansion sight unseen. It's easy money for the best brokers. Deleon is on track to do $500 million in sales this year. He's now buying a plane so he can show Chinese and Indian buyers the beautiful views of what they could be buying.
While the homebuying market has bounced back somewhat in several parts of the country, Atherton is a glaring example of how the high end of the high end of the market is surging, and prices continue to go to stratospheric heights.
—By CNBC's Mark Berniker and Josh Lipton.