Welcome to English in a Minute.Let's say you buy something.And when you pay for it,you say:This cost me an arm and a leg!Do you have to give them your arm and your leg?I hope not.Let's listen to an American English conversation to see if we can find out what this means.
A:Did you buy that new computer?
B:Yeah,I did.And it cost way more than I expected it to.
A:How much?
B:Let me just tell you it cost an arm and a leg!
When you say in American English that something costs an arm and a leg,it means that the price is very,very high.If you use this phrase,everyone in the United States will understand you.But this is an informal phrase,so don't use it in a business setting.
And that's English in a Minute.