Her decision to leave the company proved to be an 'expensive' mistake. [=a mistake that caused her to lose a lot of money]
They live in an 'expensive' neighborhood. [=a neighborhood in which houses, apartments, etc., cost a lot to buy or rent]
an 'expensive' shop [=a shop that sells expensive things]
(..) how about you forget you saw me? For old times sake? That's a no.. What did you do that made Mr. Big so mad at you? I may have sold him a very expensive wall rug that was made... - from the fur of a skunk's butt.. - Oh, sweet cheese and crackers. - Is that Mr. Big? - No. (..)2016 Zootopia