Except there wasn't, not on Apple's part. Apple just wanted to ensure it always got the "best price" from publishers. Publisher's set the prices. Any price they want. Apple was putting its customers first by demanding "best price" for access rather than see iOS consumers used and abused to subsidize lower prices for Amazon Kindle or another outlet.
This kind of usurious behavior happens in gas prices, in healthcare prices and elsewhere. Rather than the price being the price, the price is spiked in some so-called "get healthy" market areas to subsidize others or to run up profits because the companies know they can.
Unlike real world products, including books, there are no logistical justifications for publishers to charge one ebook retailer more than another. Development cost differences? Statistical noise at most. Volume discounting? It's just bits.
If anything, Apple's demand means there will be no unfair premium "tax" added to ebooks just because they're on iOS. All ebook platform users should win because the total marketplace is that much larger.
I'm sorry, but you don't understand how the publishing industry works, and loving a companies products doesn't mean their practices are always fair.
1. Apple knew exactly what they were doing and knew the publishers were looking for a way to fatten their own wallets. What this deal did was kill competition. Without it, iBooks would have been a total failure. (It's honestly not a smashing success now.) Why buy from Apple when you can shop around other retailers, have their reader apps on your device, and get the best price elsewhere? This is called PRICE FIXING. This deal and model has made it so that no matter which ebook seller you go to, there is likely not going to be any incentive to price shop as the prices are going to be the same. It's also inflated prices. There is no excuse for a hardcover book to be cheaper than it's ebook version.... and 9 out of 10 times, you can find a hardcover on sale cheaper than the ebook because physical book prices can't be price fixed in this way because they use a wholesale model.
2. You rationale is flawed. If Amazon and B&N are buying physical books from a publisher, why shouldn't they be able to negotiate better ebook wholesale prices? That's called a free market. And why should they be able to buy physical books cheaper then ebooks which have almost no cost to a publisher? A $10 ebook nets 30%, or $3. They can make $5 off the paperback book. How does that make sense?
Apple did not ensure IOS users the best price with this deal, they screwed them. Ebooks were just starting to get to a point where there was a value associated with them. Prices were starting to get cheaper than paper books.
I can take a paper book to a used book store and trade it for credit, lend it to my cousin, and I can't do that with an ebook. There's less value to the buyer of an ebook, but the prices don't reflect that. Don't compare commodities like oil to books. No one needs a fiction book... but they do need gasoline to get to work even if they're just taking a public bus.
The telling difference is when you look at brick and mortar stores with physical inventory vs. virtual inventory. The evidence of price fixing is totally transparent.