Why on earth would anyone buy a book that cannot be read on the device you already have?
By all means, All Hail to the $100 ebook -- $15 for the ebook file and $85 for the reader.
There is a reason generic DRM systems exist; they are popular enough that you are likely to already own a matching device. Only when you can read more than one or two book on an ereader is it worth buying.
That is without even getting into long-term issues like closing bookstores robbing you of your DRMed purchases.
Or how I know your book exists when it is only sold in some local ebookstore.
