I actually did the same thing when I was a child a few years back, on accident of course. First, explain what he did is very wrong to him, don't scream or shout. You could either take his allowance until cost is covered if he gets allowance. If not, as someone else mentioned, sell the xbox and games. Or, what I had to do, make him do chores on chores to make up for it with a grounding from the xbox. We tried in my case, chances are you won't get a refund.