If the plane has empty seats, the cost of adding one more passenger is minuscule, although the average cost of flying a passenger is $500, the marginal cost is merely the cost of the bag of peanuts and can of soda that the extra passenger will consume.

• 如果飞机有空的座位；每增加一个乘客成本就会更小；尽管每位飞行乘客的平均成本是500美元；边缘的价格仅仅是乘客将额外消费的花生和罐装汽水的价格.