Perhaps publishers are trying to follow the restaurant model of pricing. At a restaurant, they generally break even on the food when you factor in food cost, labor cost, building cost. They make their profit at the Bar. Alcohol is VERY profitable.
Perhaps S and S are trying to make some profit on Ebooks. Just like alcoholic beverages at a restaurant, not everyone is going to buy an ebook, but those who do provide a nice built in profit to the owner/publisher.