No way on earth we should allow seized contraband to become a revenue stream for the State. It does make some sense when you see the amount that has to be destroyed but there are good enough reasons why not.
First, if it's a copy, they can't guarantee its safety. No way this can be sold on. Second, it has to be stored until the court case, again even if legitimate it may not be sellable at that stage.
Last, is it really wise to rely on revenue from reselling the stuff. Not only is it asking for corruption, but if it becomes an essential revenue, then there's no incentive to stop the trade.