But problems can arise when it comes to verifying those international buyers. In order to schedule a showing of a $65 million or $125 million home, brokers need to know you can afford to buy the house beforehand. If you don't appear on the Forbes billionaires list, a simple note from a Swiss banker will do.
"The hardest thing for me is to differentiate the people who contact me, to find out if they're real," says Lenz. "They can get very annoyed, but I need to know they can write the check."
Ah, the check. Sometimes there is no need. After all, when an international jet-setter pays $100 million for a third or fourth home, why take out a mortgage?
Many top-tier transactions are "done in cash," says Condon.
As for which mega-mansion will sell first, it's anyone's guess. The decision to purchase a home of such caliber comes down, more than anything, to personal preference.
"Think of it this way," says Umansky. "I could put three mega-yachts in a line -- one contemporary, one traditional and one Mediterranean. I don't know which one is going to sell because I don't know which one Larry Ellison or Bill Gates is going to pick."