I missed this very interesting post published months ago:
The Cost of Self Publication, Ebook vs. Print: One Person’s Story
$3,500 for editing
$100 for a final proof
$70 for a newer version of Photoshop (eBay)
$25 for the ISBN
$2.50 for front cover image (stock photo, what can I say)
$24.95 for eBook Studio (the eReader format)
$99 to turn it into an iBook application for the iApp store*
Cost per ebook FORMAT (not including in-kind labor costs for markup): $382.15.
There are also expenses listed for print.
Still, you’ll notice that whether I had put it in print or not, editing was the biggest expense and that would have been spent regardless.
Unless you know good, professional, and free editing labor …
You cannot calculate the unit cost of the e-book because the unit price will always be as X approaches zero. You can only calculate the cost PER FORMAT (which may or may not include DRM). You have the opportunity for an unlimited number of e-book sales without further cost (not including web and shopping cart, etc.). For every print book I sell, I have to spend another $15.00. For every e-book I sell, I have to spend ZERO.
There are those who will argue with that. But we’ll see.