【原文】Ten Principles of Economics 2: The Cost of Something Is What You Give Up to Get It
【cost】成本。The effort ,loss or damage that is involved in order to do or achieve sth.成本是一种代价。
【译文】十大经济学原理1：你为了得到一物而所做的牺牲称之为此物的成本
【原文】Because people face trade-offs, making decisions requires comparing the costs and benefits of alternative courses of action. In many cases, however, the cost of an action is not as obvious as it might first appear.
【译文】人们做决策要有取舍，也就是要权衡可选行动方案的成本和收益。然而，在很多情况下，一项行动的成本并非显而易见。
【原文】Consider the decision to go to college.The main benefits are intellectual enrichment and a lifetime of better job opportunities. But what are the costs? To answer this question, you might be tempted to add up the money you spend on tuition, books, room, and board. Yet this total does not truly represent what you give up to spend a year in college.
【board】伙食费
【译文】相比较于不上大学，一个人上大学的主要收益是学习到知识，并在今后的生活中获得更好的工作机会。但是，成本是什么呢？你可能会说你的学费，书本费，住房费，伙食费之和就是你上大学的成本。然而，这些费用并不是你上一年大学的真正代价。
【原文】There are two problems with this calculation. First, it includes some things that are not really costs of going to college. Even if you quit school, you need a place to sleep and food to eat.Room and board are costs of going to college only to the extent that they are more expensive at collegethan elsewhere. Second, this calculation ignores the largest cost of going to college—your time. When you spend a year listening to lectures, reading textbooks, and writing papers, you cannot spend that time working at a job. For most students, the earnings they give up to attend school are the single largest cost of their education.
【译文】上述的计算方法有两个问题。第一，统计中的一些费用并非上大学的成本。即使你离开大学，你也要睡觉和吃饭，也需要住房和食物。只有上大学的住房费和伙食费比其他地方更加昂贵时，多出的部分才是上大学的成本。第二，这种计算方法忽略了上大学最大的成本——你的时间。当你把一年的时间用于听课，读书，写文章时，你就不能同时工作。对于大多数学生而言，为了上学而不得不放弃工作带来的收入才是他们接受教育的最大的单项成本。
【原文】The opportunity cost of an item is what you give up to get that item. When making any decision, decision makers should be aware of the opportunity costs that accompany each possible action. In fact, they usually are. College athletes who can earn millions if they drop out of school and play professional sports are well aware that the opportunity cost of their attending college is very high.It is not surprising that they often decide that the benefit of a college education is not worth the cost.
【opportunity cost】机会成本。whatever must be givenup to obtain some item。机会成本告诉我们“不收费”不等于“免费”。虽然刷微信不收费，但是这种行为浪费了你的时间，你完全可以用这些时间去工作而获得收入，这种收入就是你刷微信的成本。
【译文】一物的机会成本是指你为了得到该物而所做的牺牲。决策者做任何决策都要清楚地知道每一种可能行为的机会成本。事实上，他们的确是这样做的。大学运动员深知上大学的机会成本非常高，因为他们上大学就要放弃可以给他们带来百万美元的职业运动的机会。他们断定上大学带来的收益并不能弥补其带来的成本，这一点并不奇怪。
