cost an arm and a leg成語所屬單字legcost an arm and a legcost an arm and a leg — 慣用語慣用語1. to be extremely expensive.1.慣用語釋義花費一大筆錢；昂貴至極to be extremely expensive.例句The repairs to the car cost an arm and a leg, but we had no other way to get to work.