Right place. I would keep him if you have excess stubs to flip with. And if his purchase price is 21,000 that's what you should sell him for. Never do a Buy or sell now, only do sell/buy orders for the best stub management and to make the most off your card flipping, if that makes sense.
I work on a computer all day so i'm usually on The Show Nation website buying and selling equipment. It sells quickly and the margins are very beneficial for flipping.