Re: price point
Apple, and their suppliers, can take a longer term view. They can take a temporary margin hit as production is ramped up, knowing they'll be fine in six months once the kinks are ironed out and things are humming along.
A typical PC maker, operating on thin margins competing with other PC makers operating on thin margins, doesn't have nearly the flexibility to do this. When they do something new and expensive, they charge more for it, then when it becomes cheaper they reduce the price. They'd rather not, but their competitors will if they don't and it'll hurt them worse than the lower price.
Apple prefers to keep the same price for something over its life, or at least until it gets updated. They can do that where PC makers can't because Apple is the only vendor of products that run Mac OS and iOS, as opposed to being one of many vendor of products running Windows or Android. Apple likely plans their pricing based on a target margin over the life of a particular product configuration. That is, when they introduce a new iPad with a retina screen and the bigger backlight and battery required for it, they have a particular target margin in mind. They will undershoot that margin at first, since the components cost more initially, but overshoot it by the time the product is ready for a refresh, when components drop in price. If they plan correctly, they get their target margin. Almost certainly, their suppliers take some contractual risk as part of this too - or maybe the suppliers take all of the risk, Apple does huge volumes and can put the squeeze on suppliers as a result.
So I don't think it matters whether the cost of 13" Retina screens is lower by fall or not, what matters to Apple is the average price from fall 2012 to fall 2013 (or whenever they next plan to upgrade the product)