為什麼在「成本」定義中「最高」二字是必要的?

因為機會成本ge定義係指「在選擇過程裏，人們所放棄的可行性中，價值最高的一個」

如果無左最高二字,,就唔係機會成本..只係你放棄ge野

Cost is the highest valued option forgone. It measures the amount forgone.

If one does not choose the present option, he can only choose either one of the remaining option. Mostly likely, the highest valued option is selected under constrained maximisation. So the highest-valued alternative that you have forgone is the only option relevant for decision making, i.e. to choose either the present option or the highest-valued option forgone. Thus, what has been forgone, i.e. the cost in choosing the present option is only the highest valued alternative forgone.

In short, under constrained maximisation, the highest-valued option forgone is the only option relevant for decision making, i.e. the one constitutes the only relevant alternative choice. Anything less than this highest sacrifice is irrelevant for decision making.

2008-09-15 21:00:17 補充：
The last paragraph is the AL MARKING SCHEME answer. Others are elaboration.

For the purpose of calculation on opportunity is maximizating your utility, so you are only caring and focusing on the largest sweetens you have to give up for exchanging your wants. For example, you have an hour extra time, then you can spend this hour for watching movie or having rest Assume that you want to watch movie more than a rest. However, your mother asked you to spend this hour for studying. Therefore, your opporunity cost will be watching movie, and not rest. Since even you don't need to study but you will spend this hour for watching movie instead of sleeping; therefore, you are only give up the opportunity for watching movie to Exchange the studying.