There is. 15" laptops are the most popular size and what Apple sells in that size bracket is not cheap. It's a pretty gaping hole in their lineup really. A $1300 or $1400 15" MBA would probably sell very well, not because of weight and size but because it's a 15" screen for less than $2500. It makes more sense than the 13" MBP that's barely distinguishable from the MBA.