The impending Facebook initial public offering is pushing already-expensive Silicon Valley real estate to frenetic new highs.

The two months prior to the IPO announcement saw only 840 sales in the region. In dramatic contrast, sales in the last two months have almost doubled to 1,531, according to Guy Wolcott, the co-founder and chief executive of the company behind real estate app HomeSnap.

It’s not just sales. The median sales price is up 15 percent in the same time period, and the number of million-dollar-plus prices is up a staggering 159 percent since the Facebook IPO announcement.

These bargains won’t last

Above: $5.5 million. Only 18,000 Facebook shares!

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While that’s not a conclusive cause-and-effect connection (there’s a lot more wealth in Silicon Valley besides Facebook stock), the rising real estate prices do indicate that something big is happening. Once the IPO happens and employees’ lock-up periods expire, prices will go even higher.

Housing prices in desirable areas of California’s tech hotbeds have always been high, especially in San Francisco, Palo Alto, Santa Clara, and Facebook’s hometown, Menlo Park.

But in the last two months Silly Valley is just getting plain ridiculous. Think $5.5 million for this fairly large but hardly palatial family home (right). Or $4 million for a six year old home in central Menlo Park. The built-in wine cellar will help you recover from the inevitable sticker shock.

Fortunately, Facebook employees have a lot of cash coming. As of last year, Facebook employees owned around 30 percent of the company, worth perhaps $25-$30 billion when the company goes public.

Until the company does go public, selling those shares is difficult, but not impossible, and many have been selling privately on secondary markets like Sharespost for years.

Once the IPO happens, the biggest winners will be the earliest employees, investors, and top executives. According to Who Owns Facebook, Sheryl Sandberg will cash in to the tune of $1.8 billion, former employees Chris Hughes and Matt Cohler will take home $850 and $680 million, respectively, and current employee Jeff Rothschild will also pocket $680 million.

But even employees who joined later should do fine: According to this Quora thread, the average Facebook employee will realize about $2 million in the IPO.

“Staggering” market conditions

According to Wolcott, the current doubling of home sales is “staggering,” and the prices are continuing to rise rapidly.  “All indicators are saying this is a hot market,” Wolcott said today, “and it’s hotter the higher you go up the price scale.”

Wolcott knows these numbers because he’s the cofounder of Sawbuck, an online real estate service that competes with the likes of Trulia, Zillow, and Redfin. Eight weeks ago Sawbuck released HomeSnap: a mobile real estate app that Wolcott calls “Shazam for homes,” referencing the popular music identification service. With HomeSnap, you take a picture of a home, and get huge amounts of data: if it’s for sale, price, lot boundaries, school district, tax information.

In eight weeks, HomeSnap has been installed 115,000 times and been used to snap 175,000 homes. And Silicon Valley is one of the hottest locations. Tony Palo Alto is number one. Nearby Redwood City is number two, and Facebook hometown Menlo Park is not far behind at number 4. Could all those Facebook millionaires-in-waiting be scoping the goodies?

See below for an infographic from Sawbuck illustrating the rapid changes in the Silicon Valley real estate market.

Are you an employee of Facebook or any other startup who has used stock options to buy a house or some other splurge? Congratulations! Also, we’d love to hear from you.

Image credits: Sawbuck, AMagill