When collecting valuable items, one tactic is to just drop the magic box once the banking of the imp-in-a-box has been used up, as the profit from the items can greatly exceed the cost of the box. For example, Red dragons drop dragon bones and red dragonhide, each of which is worth several thousands of coins per item. It thus can make sense to drop the magic boxes when emptied, in order to carry more bones and dragonhides.