This was noted in another comment. A print book is about $3 more in cost (printing, distribution, returns, etc.) than an ebook. i.e. not nearly as much as most people assume.
(I note that I can order quantity one of the book I have on Amazon Createspace for $3.75 plus shipping.)
But the prices have been / are often higher.
I see that good ebooks have some extra typesetting and such, but that should be largely automated with the production of print ready copy.
How can they not save on paper, presses, covers, delivery, distribution?
Yes editing, proofing, marketing, cover design, etc., still costs.
Devices don't seem that discounted that there should be an extra load per book to post for them.
Do you have a source for eBook production costs, would be interested to look at financials vs. traditional publishing.