Behind every business movement that comes along are real people who are trying to meet the latest need of a perceived "customer". Authors are really no different. We often write books for "readers" who are no more visible to us than the characters in the stories we create. So it's no wonder we struggle to set a monetary value on our work. We can only base what we charge on our own experiences.
When I started self-publishing, I priced to be competitive with others in my genre. At the time, I didn't understand that I was pricing my new book to compete with the price of an established author's backlisted book, already several years old. While this has turned out okay for me, it might have been better had I understood the trend at the time.
The following NPR program brings up some very interesting ideas about what drives the prices and value of things, including ebooks. But don't stop listening after the ebook part. The discussion about the history of Legos is even more interesting in what it teaches about marketing success.
The Price of Things We Love