Would you pay $15 for a mass market paperback simply because it was released at the same time as the hardback?
I would not.
Like a hardcover, paperback, or trade paper edition, an ebook should have a fixed price range, based on the fact that it is an ebook, NOT on when it came out. The value of an ebook is not the value of a paper book.
No, “convenience” does not add value, it is a marketing word.
There are a lot of features a paper book will always have over an ebook. I can lend out my paper book. I can use it to prop up a table. I can sell my paper book. I can buy a paper book used.
No amount of convenience will make an ebook worth more than a paper book. Having it stored on a cloud service is not enough to make an electronic file with the text of Dune worth $15.
So here is my ebook oath, from me, a reader, a consumer, to you, the writer out there:
I promise to not pirate your work. Period.
I promise that if you are selling a DRMed text file for $10 or more, I will not buy it.
I promise to support you if your books are reasonably priced.
I promise to tell my friends about your reasonably priced books.
I promise to tell them to avoid your over priced books.
I promise to strip off any DRM on any books I buy. I will not be subject to Amazon or Barnes and Noble on whether I can read something I have paid for.
I promise that there is more to read in this life that I could ever hope to read, but I am going to try.