Why did Berk have a good laugh at Allan's expense?

（誤譯）為什么伯克大笑艾倫的花費？
（正譯）為什么伯克對艾倫大加嘲笑？

1. laugh at 嘲笑；因……而發笑

I prefer you laugh at me to my face!
你要笑就當著我的面笑！

It is important to laugh at oneself.
對著你自己笑是重要的。

Oh, cheer up! Nobody will laugh at you.
哦，振作起來吧，沒人會笑你的。

2. expense n. 損失，代價；消費；開支 vt. 向……收取費用 vi. 被花掉

at the expense of 以……為代價；由……支付費用

In that case the politicians' push for more trade may come at the expense of fair trade.
在這樣的局面下，政客們推動的貿易量的增長只能以公平貿易作為代價。

It must also be fair, not allowing one task to run efficiently at the expense of another.
它也必須公平，不能因為要有效率地執行某項任務，而犧牲了另一項任務。

People sell it, at the expense of their leisure time, purely as a means to the end of consumption.
人們以自己的閑暇時間為代價出售它，僅僅是為了消費的手段。

at no expenseat 不花錢地；沒有損失地

I will stop at no expense to obtain it.
我將不惜一切花費來得到它。

There is no happiness for people at the expense of other people.
為了自己而犧牲別人，不會不快樂。

If you cannot afford an attorney, one will be appointed for you at no expense.
如果無法負擔律師費用，法院將為你指派一名辯護律師。