What price discount in an electronic marketplace
When dealing with physical items, the purpose of discount is clearer, a wholesaler agrees to take a palletload of stuff with associated reducing packaging and processing costs compared to the ones and twos going out to the retailer and the manufacturer gets a quicker payment but at a lower return.
With the retailer, the discount to the customer is to clear old stock that isn't selling (remaindered bin), or act as lure to bring in footfall who might by other stuff (supermarkets)
With ebooks where's the incentive to discount, except to lock the buyer into returning to the same (e)store next time they want a book, or to lock them into a preferred format with the same effect. An ebook doesn't take up stockroom space, the only issue for the retailer is how many concurrent purchases and downloads it can handle.
LAst thought - with no little to no physical limit on the number of copies held, the number of available loans has to be limited to maintain the seller's market.