"Cost someone an arm and a leg" 是一个英语习语，用来形容某物价格极其昂贵，以至于购买或完成它需要付出极大的代价，通常超出预期或承受能力。这个表达方式源自夸张的比喻，暗示为了得到某物，一个人必须付出身体的重要部分，即手臂和腿，强调了代价之大。

**用法**

1. 作为动词短语：This new car costs an arm and a leg, so I can't afford it. (这辆新车价格高得离谱，我买不起。)

2. 作为插入语：I love that painting, but it would cost me an arm and a leg to buy it. (我喜欢那幅画，但买下来要花一大笔钱。)

**例句**

1. The tuition fees at private universities can easily cost an arm and a leg, leaving many students with huge debts. (私立大学的学费非常高，许多学生因此负债累累。)

2. The renovation of our house cost us an arm and a leg, but it was worth it for the comfort and aesthetics. (我们房子的装修花了大价钱，但为了舒适和美观，这一切都是值得的。)

3. That designer dress she bought must have cost her an arm and a leg; I hope she didn't go into debt for it. (她买的那件设计师裙子肯定很贵，希望她没为此欠债。)

**同义词辨析**

1. "Break the bank" - 这个短语也表示花费巨大，导致破产或经济困难。例如：The wedding ceremony was so extravagant that it almost broke the bank. (婚礼如此奢华，几乎让我倾家荡产。)

2. "Empty one's pockets" - 意思是花费所有积蓄，使某人变得一贫如洗。例如：The medical bills after the accident really emptied his pockets. (事故后的医疗费用让他花光了所有的钱。)

3. "Cost a fortune" - 形容某物价格极高。例如：The antique vase was a family heirloom, and they were told it could cost a fortune if sold on the market. (那个古董花瓶是家族传家宝，他们听说在市场上出售可能会卖个好价钱。)

虽然这些短语都有相似的意思，但"cost someone an arm and a leg"更具戏剧性和形象性，通常用于口语和非正式场合。在正式或书面语境中，"break the bank", "empty one's pockets", 和 "cost a fortune" 可能更为常见。