During the summer months, I frequent a local farmers' market most Saturday mornings. Certainly, I can buy jams, vegetables, breads, and sweets much cheaper at the supermarket. However, the foods I get at the farmers' market are, by and large, natural and not loaded down with a shitpile of preservatives.
This isn't why I do it though. I do it because when I hand over my dollars, I'm giving it right to the person who produced it.
(okay, and they make some amazing goods too)
Amazon is the same way--by the large, minus a small percentage when you sell something. So are Kobobooks, Barnes and Nobles, Smashwords, and other e-tailers. Indie authors have a fair shake when it comes to readers. They are able to bypass whatever middlemen or gatekeepers there are and go directly to the readers.
Instead of farmers having to send their goods to the local elevator or with the grandmother who bakes amazing donuts and breads, they can go directly to the people and sell their goods.