The promise of ebooks or ibooks (digital books in general) is that they will make it easier for people to read on the go. You can take an entire library of books with you on the road (or in the case of students to school) on your Kindle or iPad. Another promise of these digital books is that they will help the environment by savings trees used for printing books.
Another expected benefit, although not promised or stated, is the notion that the price of a digital book would be much cheaper than a printed book because delivering a digital book does not involve printing. It makes perfect sense. If there are any savings from the cost of printing, they would be passed on to the consumer or at least shared between the consumer and the publisher.
As it turns out, this is a complete misconception. A quick survey of the prices of a few popular books gives you the results. I just went to the iBooks Store on my iPad and search for Outliers. The price to buy and download this book that was published in November of 2008 is $12.99. I checked Amazon and was surprised to find out that this book costs only $11.69 in hardcover! The Tipping Point and Blink, another two titles by the same author cost $9.99 on the iBook Store, but cost slightly less ($9.97) on Amazon. Why aren't digital books cheaper? Where did the savings go? Did they go to Apple and Amazon?
This fact doesn't seem to impact the trend in in the success of digital books. Last week, Amazon announced that its sales of digital books is not exceeding its sales of printed books.