时间的价值本质上是一个机会成本 – 它是那个小时关闭的价值。在这个例子中，它代表了边际成本 – 个人再工作一小时的成本。边际成本的增加是一种普遍现象;一个人通常不介意工作几个小时，因为一天24小时。她还有足够的时间做其他事情。但是，当一个人开始工作更长时间时，它会减少她用于其他活动的小时数。她必须开始放弃越来越多的有价值的机会来工作这些额外的时间。很明显，她应该在第一个小时工作，因为她获得了10美元的边际收益，而边际成本只损失了2美元，净收益为8美元。按照同样的逻辑，她也应该在第二和第三个小时工作。她希望工作到边际成本超过边际收益的时间。她还希望在第10小时工作，因为她获得了＃3的净收益（15美元的边际收益，12美元的边际成本）。然而，她不想在第11个小时工作，因为边际成本（18美元）超过边际收益（15美元）3美元。因此边际分析表明，理性最大化行为要工作10个小时。更一般地说，通过检查每个增量行动的边际收益和边际成本，以及执行边际收益超过边际成本的所有行动以及边际成本超过边际收益的行动，都可以实现最佳结果。由于边际效益倾向于随着人们从事更多活动而降低，但边际成本往往会增加，边际分析通常会定义一个独特的最佳活动水平。
The value of time is essentially an opportunity cost — it is how much one values having that hour off. In this example, it represents a marginal cost — what it costs an individual to work an additional hour. The increase in marginal costs is a common phenomenon; one usually doesn’t mind working a few hours since there are 24 hours in a day. She still has plenty of time to do other things. However, as an individual starts to work more hours, it reduces the number of hours she has for other activities. She has to start giving up more and more valuable opportunities to work those extra hours. It is clear that she should work the first hour, as she gains $10 in marginal benefits and loses only $2 in marginal costs, for a net gain of $8. By the same logic, she should work the second and third hours as well. She will want to work until the time at which the marginal cost exceeds the marginal benefit. She will also want to work the 10th hour as she receives a net benefit of #3 (marginal benefit of $15, marginal cost of $12). However, she will not want to work the 11th hour, as the marginal cost ($18) exceeds the marginal benefit ($15) by three dollars. Thus marginal analysis suggests that rational maximizing behavior is to work for 10 hours. More generally, optimal outcomes are achieved by examining marginal benefit and marginal cost for each incremental action and performing all of the actions where marginal benefit exceeds the marginal cost and none of the actions where marginal cost exceeds the marginal benefit. Because marginal benefits tend to decrease as one does more of an activity but marginal costs tend to increase, the marginal analysis will usually define a unique optimal level of activity.