I beg to differ. Amazon does not have a monopoly on *anything* other than the manufacture of Kindles. However, this is just one of many types of eReaders (the actual market in question). Their goal is to maximize profit but they have to work within the ecosystem of publishers, competing retailers, and devices.
Before you snort and storm off, think about this. Fifteen years ago, Amazon was a nothing upstart going against some of the biggest and laziest incumbent retailers (I'm talking about the handful of music and book chains that dominated distribution in the US). They won that round by offering buyers what they wanted at prices that were better. As a company, they are more aware than most about how vulnerable a large incumbent can be to changes in its ecosystem. They are trying to find a product that will keep them relevant a decade from now.
What Amazon is doing is insisting on a piece of the action as the reseller (which every reseller does) and something extra for the distribution of bits. As I said before, that distribution fee may not be reasonable by any particular person's definition and is a reasonable subject for debate. <aside> Anything more than 15% above their wholesale rates (an overhead charge) seems excessive to *me* </aside> However, the only opinion that matters here is that of the publisher considering using Amazon as an e-document distributor. If Amazon's cost structure allows that organization to meet its revenue goals while keeping prices down to something consumers will accept, then it is good enough. If not, then the publisher will do something else (go elsewhere, beat on Amazon to reduce their cut, etc.). My point is that the publisher is the only one with the historical data to decide if the money is right. Some will and some won't.
This is also not to say the users are not getting screwed. That is a different question and involves what is a reasonable price to pay for an electronic, possibly DRM infected version of content you can also buy in dead-tree format. I tend to think that $9 is unreasonable for a paperback (and unconscionable for an electronic version) of entertainment prose. The question here to consider is "Who is screwing the customer?" I tend to think there is enough greed in enough places (publishers, advertising agencies, agents, resellers, authors, etc.) to spread the blame widely and thinly.