I would suggest that a 12 year old not have access to that kind of money. If it is the child's money, it should be in an account. At 12, regardless of whose money it is, the child should have to ask permission to purchase things. The child is a minor and that is how it works. If the child stole the money from parents/family, that is even worse. Either way, I would be sure to make sure they have no further access to that kind of money until they are older. The consequence should be related to the wrongdoing. Perhaps, the child should be grounded from the X-box for an extended period of time. It really depends on whether this is an isolated incident, too. Children learn from their mistakes. If the child is an otherwise well-behaved child, this could be a learning experience rather than "punishment". Best wishes.