First, it is just hubby and I play together on a LAN. We salvaged some cpu extenders, but no trader will buy them. Is there a trader that will buy them and I missed seeing them and if not, why not make it available to trade if you are playing single or LAN play?
You can't sell extenders. However, you can sell the parts needed to construct the extenders (optronic bridges and matrix). So throw them into your deconstructor and then sell the resulting parts. The bridges and matrix may get broken down as well, but you can just re-craft them afterwards.