There was an interesting article on HN today about the "wholesale model" versus the "agency model". Apple is forcing the agency model down all publisher's throats - music, movies, books, apps.
The agency model lets Apple get a fixed 30% no matter what the price the publisher chooses to sell. The retail price is in effect fixed to the wholesale price, and there are no sales and no competition at the retail level.
The wholesale model is the publisher sets the price and the retail sells it for whatever they wish. So one store can offer New York Times bestsellers at 30% off, while another store sells them fixed price, and another store has a "buyers club" that gets you 10% off everything in the store.
The variable pricing model, wholesale, is better for consumers. The fixed pricing model, agency, is better for the retailers. It's the same for publishers since they get their wholesale price either way.
Apple is smart - they think this "sell it as cheap as you can make a profit" model is not for them. It's always been their model actually.