I don't mind paying up to five dollars for an Ebook, and addictively do so.
But, I can't see these literati wanting over ten, since you can't sell it, loaning, where allowed is complicated, you can't even give it away.
Amazon, like any retailer, grinds it out of their vendors. I used to sell music tapes to convenience stores a long time ago, and they used to grind it out of me. It's unfortunate.
So, I wish that writers got a better deal from Amazon, but since there are people apparently making something out of books for a dollar or two, like Wildside Press, with public domain packages, I should think five dollars could work out for newer copyrighted books. In fact, there are a lot of titles at that price.
Do you want to make a high percentage on a few books, or a lower percentage on a (digital) ton of them ? I'd choose the latter, since exposure never hurts.