The problem with what Apple and the publishers did is that they did away with the long standing idea of wholesale pricing.
Amazon was paying a wholesale price for e-books and charging what they wanted to charge. i.e. They were paying a set price for the books and charging whatever price they wished. In some cases, it was below the wholesale price and they were losing money in an attempt to gain market share.
Apple worked with the publishers to make sure that there was a model where they all made money and consumers couldn’t get the product at a discount. Instead of the traditional practice of selling at a wholesale price and allowing retailers (Apple, Amazon, etc.) to set the retail price, the publishers set the retail price and gave retailers a set percentage of the cover.
They were colluding to shut out a lower-cost competitor at the expense of consumers.
You can make the argument that Amazon was trying to build a monopoly by driving out others in the e-book market.
The argument should be about whether publishers have a right to set a price and refuse to allow retailers to discount their products.
We already see it with other Apple products — try to get an iPad at a discount...
Except until the so-called colluding, and the new agency model went into place, Amazon had over 90% of the ebook market and is killing traditional brick-and-mortar book stores. They had already built their monopoly by manipulation of prices, shutting out competition.
Barnes and Noble's Nook didn't achieve 20% until Amazon's scam of undercharging was disrupted by the agency model. Consumers benefited by suddenly having more outlets and sustainable pricing.
A publisher has the unilateral right to set the retail price of its product. The publisher can't conspire to fix the price of its retail products.