Right now I pay for things like this but ONLY as a reward type thing. He is 13 and is starting to work more and more for money but I want him to be self sufficient on the big purchases in the next couple of years...like car, insurance, fuel, date money, etc...
If XBL is under a $100 a year then no big deal for me to fork it out but for him that $100 could go a long way towards a car payment or other aspect of ownership.