In economics, pricing is a blend of art and science. Psychology has taught business a lot about how to manipulate people into paying what the business wants them to pay. The x factor always seems to be what people perceive as the correct cost of something. No matter how much you fiddle with costs, there is a point beyond which people won't go.
I wonder that, as the various booksellers tinker with prices, readers will get used to the lower prices and stop buying hardcovers and trade paperbacks altogether. Showrooming is already a problem. The way I've been thinking about this is that books should cost a certain amount. Not only are you supporting the author that wrote it, but the editor that polished the text, the marketing that told you about the book in the first place, the agent that found the writer way back when, and all the rest of the industry.
Even though though I don't pay for a lot of the books I read thanks to my local libraries and NetGalley, I still make trips to the bookstore to by hardcover and trade paperback copies of authors I really like. I can't finish my switch to ebooks--much as I enjoy them--completely until I know that the royalties have been adjusted in the authors' favor. To me, the price of a good story is still pretty high because I know that that money I spend is not just a wage for the author and publishers' work. The price is a down payment on the next story.