He hadn't wanted to pull this particular tactic, but it was basically a trump card when it came to dealing with Lupin. The Zorua had more than the usual fondness for money, of all things. Well, and other things, but also money.
It was an interesting issue if he thought about it. As someone who professed to be a professional thief, he should have had little regard for property law. Therefore, money was useless, wasn't it? It was just a way to get stuff that was legal and legitimate.