Exactly. The publishers need Amazon, and Amazon doesn't need the publishers. They have more than enough power to be able to dictate terms.
Apple realized this and was able to bully their way to a deal that worked for Apple, and the labels had no real ability to counter Apple. Amazon has yet to do so.
Arguably, Amazon has substantially more market power now than Apple did back in the Jobs days when they were building out iTunes and negotiating with the major labels.
