arm and a leg

An exorbitant amount of money, as in These resort hotels charge an arm and a leg for a decent meal, or Fixing the car is going to cost an arm and a leg. According to Eric Partridge, this hyperbolic idiom, which is always used in conjunction with verbs such as "cost," "charge," or "pay," and became widely known from the 1930s on, probably came from the 19th-century American criminal slang phrase, if it takes a leg (that is, even at the cost of a leg), to express desperate determination.