I'm with Karlfer on this one. In an ideal situation I guess the values, trade and sale, should be the same. I generally put the trade value a little higher because if I am going to take a px on something, I will likely then have the hassle of selling the item I took in trade. The increased trade value takes account of the risk taken as the item taken in trade may not achieve the expected value on selling on. With cash there is no such risk, unless you were paid in Turkish Lira etc....