Every publisher believes that the e-books don't really compete against one another in price because each one is unique. They aren't interchangeable...someone won't say "wow, I bet I can get this same book cheaper somewhere else..."
But they are wrong.
Exactly. People might not be able to buy that particular book for less money, but maybe they can find a book in the same genre for less money. The only reason someone would be set on one particular book is either a) it's an author they know and enjoy, or b) that particular book got great reviews or was recommended by a friend.