coûter très cher

You use this phrase just like a normal verb. The subject is the expensive item. For example, Cette voiture coûte la peau des fesses. You can use it in any tense. If you bought a coffee in Paris for ten euros, you might say Ça m'a coûté la peau des fesses. It is a very active, colorful way to complain about inflation or luxury prices.

Use this when you are shocked by a price. It is perfect for chatting with friends about rent. It works great when complaining about the price of gas. Use it at a restaurant if the bill is higher than expected. It adds a touch of personality to your frustration. It shows you are comfortable with the language and its quirks.

Do not use this in a business meeting with your boss. Avoid it when speaking to someone you need to impress, like a bank manager. Since it mentions 'buttocks,' it is not for polite or formal society. You wouldn't say this to a waiter while paying. Keep it for your inner circle or casual settings. It is expressive, but definitely not 'classy.'

French people love to complain about the cost of living. It is practically a national sport! This expression appeared in the 20th century. It is a more 'colorful' version of coûter la peau des yeux (to cost the skin of the eyes). Why the buttocks? Because it is a large area of skin! It implies a significant, painful loss. It reflects the French tendency to use anatomy to describe intensity.

You might hear ça coûte un bras (it costs an arm). Another common one is ça coûte les yeux de la tête (it costs the eyes from the head). If you want to be even more vulgar, some say la peau du cul. Stick to la peau des fesses for a safe, casual middle ground. It is funny without being overly offensive to most people.