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]
(..) ...molecules realign, it becomes rigid. - What kind of shapes can you make? Can be tailored to fit any structure based on a rigid skeleton. Too expensive for the Army? I don't think they tried to market it to the billionaire, BASE-jumping crowd. - Look, Mr. Fox. - Yes, sir? (..)2005 Batman Begins