cost an arm and a leg/a pretty penny, to

To be very expensive. The person spending the money can be stated between "cost" and "a." A fancy car like that costs a pretty penny, so I definitely can't afford it! Wow, a house in that gated community must have cost Alex a pretty penny.

slang To be very expensive. A noun or pronoun can be used between "cost" and "a" to indicate the person spending the money. College tuition costs an arm and leg nowadays. I'm sick of paying rent in this town. It's costing me an arm and a leg!

Fig. to be expensive; to cost a lot of money. Mary's dress is real silk. It must have cost a pretty penny. Taking care of a fancy car like that can cost a pretty penny, let me tell you. It cost an arm and a leg, so I didn't buy it. A house that size with an ocean view must cost the earth!

If something costs an arm and a leg, it costs a lot of money. It cost us an arm and a leg to get here. But it has been worth every penny and more. Note: Verbs such as pay, charge and spend are sometimes used instead of cost. Many restaurants were charging an arm and a leg for poor quality food.

A considerable sum of money: I paid a pretty penny for that ring.

Excessively expensive, exorbitant. The first phrase is American in origin and dates from the mid-twentieth century. The source is obvious: giving up an arm and a leg to buy something is clearly too costly. The use of “pretty” to mean considerable in amount was originally British and is now archaic except in a few well-worn phrases like this one, a cliché since the late nineteenth century. It was common throughout the eighteenth century, and crossed the Atlantic as well (“The captain might still make a pretty penny,” Bret Harte, Maruja, 1885). A similar term was a fine penny, now obsolete.