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To be very expensive; to require a large amount of money.
The tuition at that private school costs an arm and a leg.
The tuition at that private school is very expensive.
I’d love to buy a house in the city, but it costs an arm and a leg.
I’d love to buy a house in the city, but it is extremely costly.
Often used hyperbolically to emphasize the high cost of something.
Do not take this phrase literally. It does not mean someone is physically losing limbs to pay for something; it is a hyperbolic way to say something is very expensive.
This idiom is informal. Reserve it for casual conversations or creative writing. Avoid using it in formal emails, academic papers, or professional settings.
The phrase likely originated in the early 20th century, possibly from the idea of paying a high price in terms of sacrifice or physical loss. The imagery of losing limbs to afford something emphasizes the extreme cost. Similar phrases like 'give your right arm' (to do something) also use body parts to convey extreme willingness or sacrifice.
This idiom is informal and should not be used in formal writing or professional contexts. It is commonly used in casual conversation to emphasize the high cost of an item or service.