Do authors get more money from ebooks or physical books?

From what I learned in college paperback get’s them more money. Ebooks are only selling the usage rights, which cost less. Paperback/Hardback/Physical books pay the author more due to a set percentage they get from each copy sold, this number is always higher than usage rights. Ebooks your mostly paying the provider for allowing you to download from their server.

Judging from what I’ve heard authors say, it seems to depend on whether the author self-published or the book was released through a traditional commercial publisher. A book that is sold and promoted by a commercial publisher is going to sell more copies, but the author’s percentage is small. The author gets to keep most of the selling price of a self-published ebook but will typically sell far fewer copies.

@Jeruba How do I find out the difference? I would assume that if it’s self-published, I won’t even have an option other than ebook, but I really don’t know.

What about smaller publishers? The book inspiring this question is published by a company that “is a nonprofit, collectively run book publisher with more than 250 titles in print.”