I made the mistake of listing a phone for sale on ebay.
Jesus christ, how these people manage to tie their shoelaces without strangling themselves to death is beyond me.
I once sold some Cisco phones unlocked for SIP.
A buyer didn't have the first idea how to set them up, didn't know what a TFTP server was or what Asterisk is, he even wanted me to send him the TFTP config files.
In the end he returned them as faulty, they were working with an Asterisk setup before eBay, and when they were returned I had them running as soon as I plugged them in. I think people buy stuff on there thinking that it would be a simple project, don't actually know how to use or configure them, then decide that because they don't have a clue what they are doing and return them. Things like that I would accept that I didn't know what I was doing and sell them on eBay, I wouldn't return them.
I actually bought the Cisco phones in bulk (20 phones) on eBay from an office clearance, I didn't know what I was doing, but I did know that they could be unlocked. I did all the relevant research and got them all working, it was for a home project, something to learn from. I knew that I wouldn't need all of them and I planned to sell what I didn't need, after using 6 around the house I really couldn't be bothered with the eBay idiots and gave 10 of them to a friend of my parents, I think the person was setting up a business and needed something for the initial setup. I've still got 4 of them spare, should any be needed elsewhere.
I'm currently selling some very basic old UniFi AP's and stated in the listing that they needed a 24V Passive POE injector, the person bought 2 of them, then asked if they actually worked, once again I replied pointing out that they needed 24V Passive POE, fortunately I'd not started packing them or printing off postage labels, but it was later that night the buyer cancelled the sale. The reason was bought by mistake, but it is another example of how people see something at a good price, don't really know what they are buying, just thinking that it looks like any other UniFi AP. The way I imagine it is that the person told someone what a great deal it was and the other person pointed out that it's old, much slower kit, even though all this is mentioned in the listing.
I think it was with Yahoo Auctions there was an escrow service would get the item, check that it worked and was to the specification in the listing before sending it to the buyer. I never used it, and at that point I hadn't started selling on eBay or Yahoo. I think it was only an option on items over £40, and the buyer had to pay the escrow cost. I think eBay do it now automatically on items over £1000.