Abstract: An up-sell and down-sell method and system that considers a ranking of the individual marginal profit/loss of adding every product SKU of a merchant to an order (or a certain subset of SKU's based on other criteria), considering not only certain traditional fixed metrics the merchant may define such as product gross margins, credit card fees and labor costs (the cost of the pick)—but most importantly, variable packaging and shipping costs as well. In particular, the invention focuses on the packaging and shipping ramifications of up-selling every potential merchant SKU (or a certain subset of SKU's based on other criteria) to customer's order and down-selling each item already in customer's order.