That's because according to NPD, in June, 91 percent of the market for computers that cost over $1000 belonged to Apple.
Sure, it helps that Apple only sells two computers under $1000—the white MacBook and Mac mini—so if you get a Mac, it's probably going to cost over a grand. In fact, the average selling price of a Mac is $1400. But, consider that Apple claimed just 66 percent of the $1000+ market in the first three months of 2008, and 88 percent in May of this year.
It also means that people just aren't buying super tricked-out PCs—which is something Microsoft courted with its Laptop Hunters ads, showing how cheap PCs were compared to Macs. To wit, the average selling price of all PCs in June was precisely half that of Mac: $700. (For Windows notebooks, sans netbooks, the average selling price was $569.) Which suggests there are way more Laurens than Giampaolos in the world.
Update: It should be noted, however, that these numbers are for retail—not for business purchases or PCs people built themselves.