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The rich are only getting richer, and they've got the real estate to prove it.

For the world's super-wealthy -- not your Angelina Jolies and George Clooneys but your billionaire CEOs and various magnates who are way wealthier than those peons -- the price tag for an appropriate home goes all the way to $1 billion.

Some uber-rich buyers, such as Brazilian-born philanthropist Lily Safra, buy historic estates and add a few personal touches, like their own helipad. But many build a custom palace from the ground up.

Bill Gates spent seven years and a few million dollars on his ultra-nerdy Xanadu 2.0 compound overlooking Lake Washington, and his personal seal is on everything from the high-definition monitors with changing art to the high-tech underwater sound system in his pool. Investor Ira Rennert's neighbors in The Hamptons weren't too happy when he decided to build a $245 million, 110,000-square-foot manse, but he got his bowling alley and personal power plant all the same.

Here are 10 extravagant homes with owners who really understand luxury