I foresee the stock price getting a beating today. There goes the margins.
Frankly, the retinas are all overpriced to begin with. This is just the start of a return to more normal pricing.
In the old days Apple gave feature bumps while maintaining the pricing. The retina price bumps were pretty severe. Even with this price change they are still $400-600 over what they should be.
Not a lot of people are going to buy a $2,200 15" notebook (let alone a $2,800 one). They need to be in the $1,600 to $2,200 range and even that is a stretch over a windows laptop.
Its a problem that Apple is making retina sound mainstream rather than exotic so people can complain the margins suck when they reduce the entry level price of a 15" laptop to ONLY $2,200. This may be a case where the cost of the tech is just not such that it can make an affordable product.
I guess you can still find a $4-5k tv but no one's going to buy that either for whatever extra features it may claim to have.
[It's also very possible that production costs are going down / yield going up as more retina screens are made.]