A simple and common example is found in the hotel business. Room service menus commonly include a statement such as “A $2 delivery charge will be added to each order.”Why not adjust the listed the listed prices of all items on the menu by just enough to recover delivery costs, rather than apply a separate delivery charge? The reason is that an arbitrary allocation would be required to calculate the amount of delivery cost that should br added to each item. Should it be the same for a $1 item as for a $30 item? Should it be large enough to justify delivering a single-item order? The answer is that the price necessary to justify the costs of delivering an order should be applied to each order, rather than applying some fraction of it to each item.