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]
(..) I'm the one who buys it. I know how good it is. When Bonnie goes shopping, she buys shit. I buy the gourmet expensive stuff... because when I drink it, I want to taste it. But you know what's on my mind right now? It ain't the coffee (..)1994 Pulp Fiction
(..) Now, the first two are the same... a gram. Those are friend prices. But this one is a little more expensive. LANCE: This is a gram, but when you shoot it... you will know where that extra money went. Now, there's nothing wrong (..)1994 Pulp Fiction