From a book blogger turned publisher.

Relevant to recent discussions in particular is (bold in original):

Good cover art costs money

An excellent cover artist, with a track record of working on novels that then sell like hot cakes, can charge a LOT of money for their work – and so they should! They should be amply rewarded for such a visible part of the novel, for taking an art brief and conversations with the art director and turning it into something stunning. For producing something that can sell the book on its own, without any access to what is within the novel. […] And guess what? That money spent by the publisher on a cover happens whether or not the novel is print and ebook, or ebook only, so there is one of your reasons why ebooks are charged at a certain level.

FWIW, it’s not entirely unlikely that a good cover–particularly for a debut or midlist genre title–costs more than the advance money offered to the author whose book it graces.1 Covers is Srs Bizness.

  1. This isn’t a complaint. A decent book can earn out an small advance and keep providing revenue to the author in a way a cover can’t. []