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]
(..) That's what Mr. Kesner is here for. Many times these decisions are left up to the courts but that can be very expensive, Frank people fighting over their children. Nobody is fighting. Look at me, Frank. Nobody is fighting. (..)2002 Catch Me If You Can