I agree with everyone else that you were fair and responsible. It's not like you pitched a fit and told him how horrible he was. You gave him consequences and even a choice for how to correct the problem. I think you did a great job. I feel sorry for his parents who at 8 aren't teaching him consequences or financial responsibility. Now is the ideal time! They will pay the price for that later when he is a teen and doesn't understand why taking a razor to his $50 jeans is not a bad thing.
You did great!