You have to factor in all expenses. too many people don't even figure in something as simple as the shipping they pay. Imagine how rich you get LOL! A gun costs $125, mark it up 10% to $137.50, but the postage to get it cost $ 25. You'll be a millionaire by next month.The big question would be how a business costs a product. The actual cost, or do they average all of their overhead and put a portion of those costs onto each of the items they sell.