Interesting article
here
Apple's laptops are excellent, but the bulk of sales are in the 500-1000 range. So, they need to be there. I'm sure there's some elasticity between $500 and $1000 shoppers. Not all of them, but at least a few people who set out to spend $500 can be convinced to spend $1000 if a product really wows them.
I'm guessing $500 is probably too low to offer a high enough standard product, at least new. Based on nothing more than my own observations of people in coffee shops and libraries, Apple probably owns the tiers between $1300 to $2000+. If they become a permanent fixture in the 699-999 space, WinPC makers should worry.