At first sight, this may appear like a greedy way to ensure high profits. These publishers claim that their costs of editing, advertising etc are so high that it costs them as much to produce an electronic book as a print one. But I think it's more than that, I think it's about control.
Over the years, the biggest publishers have almost entirely gained control of the publishing industry. They've been able to do this because they buy not only advertising in the media but also virtually all the display space - and even shelf space - in high street bookshops. With very few exceptions they also control what books get reviewed in the national press. Very simply, the big publishers decide what books readers will buy and read (even though many readers don't realise this) by ensuring these are the only books readers get to see or to hear about. Of course, many more books are produced independently by author/publishers or small presses. But however respected these small publishers are, readers will find it a challenge to find their books, relegated as they are to the back shelves (if they are stocked at all). Similarly, the big publishers command the stock routinely bought by libraries.
Now, whilst the biggest publishers have control over the market of printed books, their domination of the ebook market is not guaranteed. For the first time, books from all sources are equally and affordably available. Readers are no longer restricted to the small percentage of books displayed to them in the high street, neither are reviews restricted to those written by the national press, any customer can write one.
The response of some of the big publishers to e publishing is to agree, among themselves, to fix their prices. And while this drives up the average price of an e book and raises the cost readers expect to pay, it also does something else. If their is no financial advantage to buying a book in electronic form then many readers will buy it in print. And if they can ensure the demand for a high volume of print books, the big publishers can maintain their control of the publishing industry.