Not exact matches
The iPad is quite a bit heavier
than the Kindle (think
hardcover versus paperback, though that comparison isn't quite right), and its backlit LED display couldn't be more
different.
So the
hardcover version has a
different ISBN
than the paperback version; the eBook version carries a
different number
than the large - print edition, and so on.
In our heads, at least, readers tend to view ebooks as a
different entity with a
different price point
than a physical book, especially
hardcover.