A big part of it is psychological - when I was at the Apple store last night, people were waiting in line to play with any and all of the Apple products. Whenever someone would move away from something, another person would jump on it without knowing or caring what it was. If a consumer sees everyone around them buying a product, chances are they're going to want that item too. It's like peer pressure for the consumer market, you buy things to be cool (of course this applies to everything, not just Apple).