How much do you allow your kids to spend of their own money?

Last year, my son turned 8 and got $160 in cash from various presents. I thought it was a good time to teach him about money, so I created a "Bank of Dad" spread sheet, that shows the money he gets, the money he spends, and what his total is. I even give him 2% interest a month to encourage him to save. This worked great, and he's accumulated over $400 now from holidays and interest.But now he wants to start spending it, specifically on in-game items in the video games he plays. I'm pretty sure that, given the chance, he'd blow through the whole $400 in a weekend just buying skins and gems and stuff. I'm reluctant to let him do that because it's a frivolous purchase he'll enjoy for a couple minutes before he gets bored. On the other hand, it *is* his money, and if he had been spending it as it comes in (e.g., he gets $20 from grandma, he buys $20 on games), I probably would have allowed it. Plus, the people that give him cash for his birthday intend for him to buy what he wants with it. In general, I feel kind of sleazy not letting my kid spend his own money.What do you think? Should I impose a limit, like he can withdraw $50 a month for whatever he wants? via /r/Parenting http://bit.ly/2GFY2mU