There is one serious problem with this reasoning though. A realistic scenario might be that somebody decides that they want to buy your app and then compares th

There is one serious problem with this reasoning though. A realistic scenario might be that somebody decides that they want to buy your app and then compares the price at a couple of different app stores and decides to buy it at Amazon because there's a 10% discount but would have otherwise bought it elsewhere. In this case Amazon would have gained profit from the discount while you would have lost it. How this ultimately plays out for the developer is hard to predict because it depends on how the market develops. If the Amazon store becomes very successful and their audience shops there regardless of whether or not there is a discount then this effect will be small. The terms guarantee that users will only find discounts at Amazon and this will make them less likely to check other stores when they find an app at Amazon even if it's full price. If that's how customers behave then the optimization will stay more favorable for the developer.