I have several Kindle editions of my books and one of them is selling very well, at least by my measure of success. All of them sell at least a few copies each month, some months more than others. So far, I have only one of my print books available for sale for the Barnes and Noble Nook. It might be my one and only.
It has yet to sell a single copy.
I usually use the Kindle conversion service offered by CreateSpace because of the low price, $69. I did have one book converted by eBookArchitects and was very pleased with the results. The service from eBookArchitects does cost more but you receive converted files for both the Kindle and the Nook.
Since I had planned to use eBookArchitects anyhow, it made no sense not to set up an account with Barnes and Noble and offer the book as a Nook title. The Kindle version of the book has sold enough to pay for the conversion so I am happy.
I am still waiting to sell a copy for the Nook. I guess I will have to break down and buy a copy myself for my wife's Nook.
Cost is always a concern for me in my "business decisions" and I am certain it is for other authors who self-publish. If I am not going to be able to sell my books via the Nook, is it really worth the extra money to have eBookArchitects do the conversion? Please note, there is nothing wrong with their work, the customer service and I have only good things to say about eBookArchitects.
CreateSpace is simply less expensive. Kindle conversions done by CreateSpace have their own issues. CreateSpace will not do the conversion unless the book has already been added as a print-on-demand print book. Nor will CreateSpace do conversions for the ePub format since it competes with the parent company Amazon's proprietary Kindle format.