The problem with the complimentary goods model is that it depends on a certain amount of proprietary between the complimentary goods. But what happens when someone makes a complimentary good that is interchangeable, and breaks the proprietary; and then undercuts your price.. You are screwed racing to the bottom of profit margins with a competitor, and then you have 2 items which are low margin.
It depends on either proprietary lock in, or a service integration so good that you don't want to buy the content anywhere else.
I'm perfectly capable and willing to pirate any ebook I want to read, but most of the time I just buy them in the kindle store because it is so much more convenient. Amazon doesn't have to race to the bottom on content pricing because their services have value.
