Well the featured app of the day is sold for free, which means a lot of people will be downloading it. And when the app is sold for free according to Amazon TOS

Well the featured app of the day is sold for free, which means a lot of people will be downloading it. And when the app is sold for free according to Amazon TOS, the developer gets 20% of the list price. So if the volume of downloads is immense then you should be able to pocket a decent amount of cash from the sale. Will have to wait a while for the stats though.