The house must have cost her an arm and a leg.
相传第一次世界大战
军人最重要的就是支撑自己作战的胳膊和腿了
所以，这个俚语后来就形容代价很高，
或是指“很大很大”的一笔钱，一般与cost连用

Uncle Bear: You got a Maserati? The new car is really wonderful.
你买了辆玛莎拉蒂？这车真实太酷了
Rose: Yeah,the price of it is also wonderful and I really have paid an arm and a leg for it.
必须的，它的价格也很酷，我为了它几乎倾尽所有。
Uncle Bear: So why do you buy so expensive a car?
你干嘛非要买这么贵的车啊？
Rose: Simply beacause it is cool.
因为它比较酷呀~
Uncle Bear：You are so cool, too.
……你确实很酷。