"Bundling is an age-old merchandising technique in which customers are offered a discount if they purchase two related products. In the case of books, it’s a combo of two formats, print edition and e-book. Though the technical barriers to delivering both in one transaction are coming down, the real issue is how much to charge for the bundle."
In this article, Richard Curtis offers several bundling strategies, though he personally believes that the ebook version should be included free of charge with the purchase of the print edition. So, why do we have to choose between print and digital?
More details in: Bundling: Publishing’s Next Battleground at this link: http://curtisagency.com/blog/2010/08/bundling-publishings-next-battleground.html