Anyone who buys something from someone else, but especially a professional like a pawnbroker, has a duty to make sure the goods they're buying aren't stolen. Failing to do that is a crime in many countries ("handling stolen goods" in UK parlance). The very least the pawnbroker should pay is the cost of whatever they're out of pocket for, but really they ought to be facing criminal charges. People being willing to profit from stolen goods is what keeps people stealing. If no one was willing to buy something that had been stolen then people would stop taking things (or at most they'd steal what they need themselves).

Perpetuating criminality is in no way a good thing.