" To cost an arm and a leg" means to be really expensive.

“花了一大笔钱”意思是非常昂贵。

To cost an arm and a leg, that means to be very expensive.

“花了一大笔钱”，意思是非常昂贵。

The saying " to cost an arm and a leg" may have come from soldiers returning from war.

这句表达" to cost an arm and a leg" 可能来自于从战场归来的士兵。

The other expression is to cost an arm and a leg. Here, the verb " cost" is more passive.

另一个表达是to cost an arm and a leg。这里，动词" cost" 比较被动。

The first one is " to cost an arm and a leg." To cost an arm and a leg.

第一个是“花费一条胳膊和一条腿”。花费一条胳膊和一条腿。