This a sore spot among many of us who read ebooks. The situation you describe is not limited to Amazon or to technical books. The other major bookstores also have ebooks of various genres priced at or above paperback, and in some cases, hardback prices. For books that were published in print before ebooks became popular, I can buy into the theory that the books need to be retyped (or scanned) into a document design program and published anew as an ebook. But for books that are currently hitting the bookshelves in brick and mortar stores the electronic files already exist. Someone needs to explain to the publishers a concept called single sourcing wherein the text is stored in a database and can be exported to various formats for printing and/or for creating digital editions. With single sourcing, spell checking, grammar checking, and general content editing need only be done once. Formatting will be required for each different addition.

Ebooks are still in their infancy and I guess it will take a long time before publishers figure out how to economically create both printed and digital editions from the same source files.

You are absolutely correct that ebooks in theory should be cheaper to produce as there are no printing materials to buy, no printing production costs, no shipping costs, etc. The overhead costs should be considerably lower for ebooks. However, I'm sure publishers worry that ebook sales will undermine printed book sales if the prices for ebooks are way below those for their printed counterparts. I'm no economist so I cannot speculate on whether that is a valid concern. But I think if they crunch the numbers and find out how much it costs to produce an ebook and add to that the profit they wish to make, the costs of ebooks could be cheaper than they are.

Another problem that haunts ebooks is that publishers don't seem to edit them very well. You see a lot of typos in ebooks. This is mostly in ebooks that are produced long after the printed editions were released and thus require re-entering or reconstructing the text. Publishers often use OCR programs, but fail to adequately edit the results.

BTW, when I use the term "publishers" I'm not referring to Amazon, Sony, Barnes and Nobles, etc. Those are book sellers. I'm referring to the publishing houses like Penguin, Oxford Press, Harper Collins, etc.