People here don't seem to get the different models.
The WHOLESALE model that Amazon prefers is essentially the same as any other good you purchase at a store. The store pays the wholesale price and then sells it at whatever price they want. MSRP's are still set by the manufacturer but the retailer can choose to offer any kind of discount they want, for whatever reason. For example, a book publisher (or in this case an ebook publisher) could set their MSRP at $15.99, and charge a wholesale price of $11.19 to the retailers. But the retailers are still free to charge a lower price if they want. That's the beauty of competition. In many cases, Amazon was willing to charge only $9.99 for the ebook, taking a loss on the sale in order to get customers to the store and potentially buying other items.
The AGENCY model that Apple uses for the iBookstore (as well as the App store) essentially takes the retailer out of the equation. The publisher (or app developer) sets their own pricing, determines when and if something goes on sale, and Apple gets a cut for acting as the seller's "agent" in the transaction (processing payments, allowing the item into their store, etc.) In the above example, the publisher could set it's price at $15.99, and Apple would pay them 70% ($11.19) for each one sold -- exactly the same as the wholesale model. The difference is that the only one who could choose to put an item on sale is the publisher -- Apple isn't acting as a traditional retailer, merely as the publisher's agent.
So, while the publisher makes the exact same amount in both scenarios, the agency model produces higher prices for consumers -- Apple's 30% can't be changed, while Amazon, under the wholesale model, can sell books at a loss if they want. The publishers can complain all they want about Amazon's pricing "devaluing" their product (despite the fact that they'd receive the same amount of money for each copy, and, logically, Amazon is going to sell a lot more copies at their lower price to consumers), but, really, publishers are just scared of Amazon becoming even more powerful -- eventually demanding lower wholesale prices. This is the way Walmart behaves. They become far and away a manufacturer's biggest retailer, then start demanding price cuts once the manufacturer can't survive without them.
I don't know if Amazon plans to do that or not, but I do think Amazon has a much better grasp of what electronic content (without any production and distribution costs that applied to physical items) can sell for, than do the book publishers. In other areas (particularly music), it was Apple who had to tell the "don't-get-this-whole-internet-thing" executives that their product wasn't worth what they thought it was, but, by selling at a lower price, they could sell far more product, and make more money in the end.
Anyway, since I can read Kindle books on my Kindle, iPad, Android tab, MacBook Pro and Air, and desktop, I'm looking forward to prices going back down. Apple makes a ton of money in other areas -- they don't need their bookstore to be super-profitable in order to be the most successful company on earth.