“机会成本”这个词里的“成本”，我觉得更符合经济学对成本的定义：成本是放弃了的最大价值。
机会一旦出现，意味着在这一刻，你原本的状态会“凭空产生成本”。也就是说，即使你维持原样、不做任何动作，与之前相比，也已经凭空产生了成本。
一个新机会
比如，你原来在中国正常地工作着，日子过得舒心。突然有一个新机会出现：“你可以到美国工作。”
这时，如果继续在中国工作，就凭空产生了一个“成本”：到美国工作和生活可能创造出的美好生活。
当然，到美国工作和生活也有成本：继续留在中国本可以拥有的舒心生活。
为什么多数人选择不动
一般人遇到这种状况，选择继续在中国工作和生活的更多。为什么呢？因为到美国工作和生活有不确定性。“美国的美好生活”是未来的事，要靠想象力才能看见。大多数人一想到其中的麻烦，就会害怕，觉得还是老老实实待在原地最好。
其实，待在原地，大概率成本更高。为什么？
因为如果一件事值得认真讨论和辩论，它大抵是在指向某种更好的可能；否则，可能根本不值得讨论和辩论。
现实中，我们仍然要看到，大多数人会选择原地不动。因为选择行动，首先需要勇气；其次需要应付各种琐碎事、麻烦事的耐心，这很消耗人；第三，结果仍然有可能不如设想，使人后悔。
写完以后
我写完这篇文章后，把它发给了 Roy。她和我分享说，有一次她和朋友 Ari 交流一个工作机会时，也曾试着和他讨论“机会成本”这件事。
一个经济学概念，只有进入真实的选择，才真正有了意义。
English Translation
Opportunity and Cost Are Twins
In the term “opportunity cost,” the word cost seems to me especially true to its economic meaning: cost is the greatest value we give up.
Once an opportunity appears, our original situation suddenly acquires a cost. Even if we remain exactly where we are and take no action, doing nothing now carries a cost that did not exist before.
A New Opportunity
Suppose you are working in China and living a comfortable life. Then a new possibility suddenly appears: you could go to work in the United States.
If you remain in China, a new cost has come into being: the better life you might have created by working and living in America. Of course, going to America has a cost as well—the comfortable life you could have continued to enjoy in China.
Why Most People Stay Where They Are
Faced with this choice, more people will continue working and living in China. Why? Because life in America is uncertain. The possibility of a better life there belongs to the future; it takes imagination to see it. For many people, the difficulties come to mind first. Fear follows, and staying where they are begins to feel like the safest choice.
Yet staying where we are will probably carry the greater cost. If a possibility is substantial enough to deserve serious discussion and debate, it is likely pointing toward something better; otherwise, it might not be worth debating at all.
Still, most people will choose not to move. Action requires courage. It also requires the patience to deal with countless small complications, which can be exhausting. And after all that, the result may still fall short of what we imagined, leaving room for regret.
Whatever we choose, it is worthwhile to think deeply enough to understand that opportunity and cost are twins.
After Writing
After I finished this essay, I sent it to Roy. She told me that when she once discussed a job opportunity with her friend Ari, she had also tried to talk with him about opportunity cost.
An economic idea becomes truly meaningful only when it enters a real decision.