They're not. You can get custom machines from www.powernotebooks.com, and their prices do beat both Apple's and Dells.
I also recall the press release when Asustek won the contract for Apple's MacBook... though I don't remember whether it was Acer or Crown that won the contract for the MacBook Pro.
I am not saying that other manufacturers are not capable of building stuff that way. But they don't let you assemble your desired PC via web. OK, except maybe for powernotebooks, but I don't know them well enough to trust them yet.
I also recall the press release when Asustek won the contract for Apple's MacBook... though I don't remember whether it was Acer or Crown that won the contract for the MacBook Pro.