It's extremely easy to sell things on Ebay. What.
What is difficult? Mailing?
Sold all of my 3DS games and then some on Ebay. People will buy anything. I sold the box to my Pokemon Y game. Not the game, literally the box and someone bought it.
At one point 360s were right down in the prices everywhere. It is actually higher now than it was at one point when the 360 was current, presumably as people realise it aged well, has a great library and much of said library you can pick up for next to nothing.
Between RRoD, live bans, new models, offers for new ones (even ignoring bottom price arcades/hdd less models they came with phone contracts, insurance, credit cards, I think I saw one as a sweetener for a car loan once, loads of the predatory student botherers...*), a fairly high level of market saturation (give or take the wii it was the market leader with the PS3 taking years and years to come close to catching up, lead platform for most things of that era, kind of had some exclusives worth speaking of and first through the gate in most respects, to that end lots of people had them), a lack of video features (sure, I will have that PS3 just to stick in my room as a BD player but you mean I can do DVDs and netflix's new crappy video streaming service on my crappy internet? peh), shops like gamestop and whatever being massively overstocked on second hand ones and more besides the price for the second hand market cratered. To that end you would stick it up, wait a week or so, deal with time wasters and low level con artists and end up maybe selling it, and if you did then for probably under $50 (maybe not 1TB with games and that might have been a bit of a comic exaggeration but not just fat arcades without a hard drive and power supply). If EB offered a token sum it might have been worth it rather than dealing with the hassle, especially if you were only going to buy more games with it.
*the 360 was an easy enough device to sell (it was great after all) but some marketing groups did a stunning job in getting them in those sorts of offers. I might have to look into that one day.