I wish to sell my Nuendo 7.1 + NEK and my Nuendo 6.5 + NEK licenses to later change them for two Cubase 8.5 licenses, due I do not need the new features. Knowing all the procedure for sell the licenses, and knowing I need to send the eLicenser dongle, I ask for your advice to know where to advertise them and which price could be adequate.
You can use this forum, and Gearslutz is okay. I sold a software license there. Ebay probably is your best bet though, since it has the larger audience and affords protection to buyer and seller.
You can experiment with pricing there if you use the fixed price format.