I think the main point of the developer is to clear up a misconception about Amazon's app store (which I also had until I saw this story). Many people assumed that Amazon would still pay the devs 20% of list even if it the free app of the day. Now that I know the nitty-gritty how it actually works I understand why it's actually 0%. If Amazon reduced the price w/o the dev's agreement, he would get 20%. In this case, though, the dev was asked if he wanted to see his app as free app of the day, i.e. you had to opt in. 0% revenue for that is a fair price since in return you get a lot of free exposure, that you, as a dev, have to know and understand how to make the most of it.