Allow for item cost to be set as a percentage of sale price. ideally on both an item specific level as well as a general level or based on category or label. I buy and sell
hundreds of trading cards of which there are hundreds of thousands and trying to make a new item on the fly for a card that I may never sell again just so my profit margin sheet is accurate is impossible. I currently use the variable price marker but have the cost set to 0 because the price range for these cards varies wildly and setting a cost screws it up even more.