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]
(..) Oh,boy. What now? Well,there's some value to taking a multivitamin,but the human body can only absorb so much. What you're buying here are the ingredients for very expensive urine. Well,maybe that's what I was going for. Well,then you'll want some manganese. Well,that was fun. (..)2007 TvShow: The Big Bang Theory Title: The Luminous Fish Effect Season: 1 Episode 4