Never give up your old office equipment as a “trade-in.” You’d do just as well to give it away.
Truth be told, at the last company I worked for, we had a set policy of destroying any competitive equipment traded in, rather than see it reappear on the market. Watching perfectly good, three or four year old high-end reprographics equipment rendered “non-competing” with a sledgehammer before being shoved into a compactor week after week gave me a sick feeling in the pit of my stomach – especially since the most valuable stuff was being “upgraded” (more of a lateral move, really,) so that the government organizations that owned them wouldn’t have their budget scaled back the next year. “Use it or lose it.”
Anyway, we took those babies in, and except in rare cases (mostly colour copiers,) where it was considered worth the time/money to ship them to a distant market, they went straight to the scrap-heap. You know any “trade-in value” they had was strictly chimerical.
If it’s too much of a hassle to sell them for fair value, donate them to charity and write it off – you’ll still come out ahead.