https://marco.org/2010/02/01/just-before-apple-announced-the-ipad-and-the
Just before Apple announced the iPad and the agency deal for ebooks, Amazon pre-empted by announcing an option for publishing ebooks in which they would graciously reduce their cut from 70% to 30%, ‘same as Apple’. From a distance this looks competitive, but the devil is in the small print; to get the 30% rate, you have to agree that Amazon is a publisher, license your rights to Amazon to publish through the Kindle platform, guarantee that you will not allow other ebook editions to sell for less than the Kindle price, and let Amazon set that price, with a ceiling of $9.99. In other words, Amazon choose how much to pay you, while using your books to undercut any possible rivals (including the paper editions you still sell). It shouldn’t surprise anyone that the major publishers don’t think very highly of this offer.