Although the average cost offlying a passenger is $500, the marginal cost is merely the cost of the bag of peanutsand can of soda that the extra passenger will consume.

• 虽然每个顾客的平均飞行成本是￥500，额外顾客所消费的仅仅是一袋花生和一罐碳酸饮料的边际成本。