If I had to guess I would say it is a pricing signal to its competitors (Kindle, Nook, Sony) saying that if they try to compete on price, Apple is prepared to willing to drop iPad prices. It is the old prisoner's delimma on pricing - Apple is trying to establish a cartel price and scare the other participants from defecting.
It's not a bad guess. Oligopolies can be maintained for quite some time with the right signaling games. On the other hand, I'm not sure how credible a signal they can send. Apple may eventually make most of its money from content, but right now it's a vendor of shiny hardware, which it sells at a hefty premium. Amazon doesn't need to command a premium price in order to protect a brand image; they're a discounter, and that's why people like them. If Apple starts getting into price wars, it's heading into uncharted and dangerous lands.
This doesn't resonate for two reasons:
1) By all indications, the Kindle is a lower cost platform (~$185 according to iSuppli) and;
2) The primary purpose of a Kindle is to read e-books which virtually guarantees Amazon will further profit from related book sales. Apple's iPad has no such assurance of driving additional revenue since it's a far more versatile device.
In other words, Amazon can easily afford to just break-even on the Kindle as a distribution mechanism for its e-books and it has the cost structure to drive a far lower break-even price than Apple.
The iPad is hardly more than a 9" iPod Touch and is effectively locked into the iTunes model. I doubt Apple is worried about where users will go for content, assuming they can first convince people to buy the thing.
Apple has never profited from content (cartel control of the distribution channel protects hardware margins). It's rather amazing that book publishers don't realize that Apple's pricing control on individual MP3s was only (marginally) undermined when the first major competitor entered the space... Amazon.
Apple's products play MP3s from anyone. The iPad's book reader will be able to read the open standard ePub book format.
How is that being "Locked into the iTunes model"
"If Apple starts getting into price wars, it's heading into uncharted and dangerous lands."
I haven't seen anyone mention that Apple is alone in mass-market electronics retailers (AFAIK) in not cutting prices on models. Instead of discounting products as they get older they keep the price point the same an introduce new models with upgraded capabilities. Getting into a price cutting trend with the iPad could spill over into other products lines, to their detriment.