Ebook pricing is contentious. Consumers expect prices to be lower than print books, largely because ebooks have long been a clearly inferior product to print. If you want to change that price expectation, you have to make ebooks clearly as valuable as print, just in different ways.
Amazon has long pushed for a maximum $9.99 retail price point for mainstream books, especially bestsellers. Big publishers like Macmillan have publicly resisted that, aiming for $15 or more. Decide for yourself. Experiment by pricing sets of books differently and tracking sales over time.
The real issues have more to do with the wholesale/discount models, which determine how much you get back from a sale.