They are getting a little carried away with their pricing. Similar to many other products, when they feel it's positioned to compete with something - they adjust the price to suit also.
They would make a killing if they sub priced it/them, but tbh, even tho it's thin, I'd fancy a new Macbook for <$999, not the Air for me tho. Being able to stick it in an envelope isn't one of the major aspects I look for in a laptop.