For buying an ebook, cheapest is almost always the best option - perhaps a better term might be "least overhead". There's very little actually needed, for eboo

For buying an ebook, cheapest is almost always the best option - perhaps a better term might be "least overhead". There's very little actually needed, for ebooks - it could literally just be a plugin for e.g. goodreads, with a "buy this book" button and then it triggers another plugin to send the ISBN to calibre or to download a torrent or do whatever you normally do with your ebook. The point is, the only part the shop really needs to handle is payment. And by "handle" I mean "delegate to paypal etc".