It seems counter intuitive, but I think it has to do with the opening up of the ebook market. Several years ago, Amazon offered the only decent ereader in town--the Kindle. Thus, given the limited market, they could dictate price and keep the market price low because there wasn't much demand.
Fast forward several years and each of the major bookstore chains offered their own ebook reader (Nook, Kobo) and tablets started offering ebook experiences--either through Amazon/Barnes and Noble/Kobo apps or the tablet creator's own ebook reader (iBooks). The market explodes in terms of the number of devices people now read on, and publishers start treating ebooks as an accepted way of offering content--with that comes the high costs in terms of marketing, promotion, post-production costs (do they do anything special for ebooks), that kind of thing.
Fast forward several years and each of the major bookstore chains offered their own ebook reader (Nook, Kobo) and tablets started offering ebook experiences--either through Amazon/Barnes and Noble/Kobo apps or the tablet creator's own ebook reader (iBooks). The market explodes in terms of the number of devices people now read on, and publishers start treating ebooks as an accepted way of offering content--with that comes the high costs in terms of marketing, promotion, post-production costs (do they do anything special for ebooks), that kind of thing.