I've been in the publishing industry in some capacity for the last 17 years. You may be surprised to learn that the "immensely different" costs are not that immense.
Following a book through the author's writing, agent, publishing house, to store, the only pieces you remove from the printed equation is the physical paper & ink and physical distribution.
There are other comparable costs added into the equation for ebooks: licensing fees for the owner of the ebook format, fees to distribution companies (ie. Lightning Source), additional cost of reformatting for ebook vs. print.
I'd be startled if the cost difference between paper and digital was more than 5% of the book's total cost to produce at this point in time, even for the large publishing houses. In my case, working for a small publisher, it would actually cost us more per book to follow that route. As such, we release our work in open formats without DRM to minimize cost and we hope our customers respect that and refrain from widely distributing our work.
I'd be interested to hear experiences from others in the publishing field.