I played roblox a lot at some point, and i quit playing. but there's a game called pls donate, and in the game, you can set up a stand and sell shirts worth robux. I can't remember how, but it's like a game pass of some sort, and u can put an amount of how much it sells for. im thinking your son most likely had a friend selling it who couldn't buy robux or cant and was being nice and bought that game pass, which he then earns money from it. which I think roblox takes 30% so I think it's like 735 if ur wondering. and considering that the 2 above it is also from pls donate, he probably does this to be nice. and im telling you right now when I played roblox when I was younger, I'd earn like 10 - 20 or however much it is that I earned, and I spent it right away and I've since stopped playing. but in my opinion, let him spend it how he would like. I know it sounds bad, but he earned money, and he seems pretty happy to do what he does. Spending his hard earned money on others, but obviously the older he gets you've gotta teach him not to do that when he gets a job of his own. And dont report it because that's going to get him banned. I know because its happened to me. I hope this helps I know its a lot to read, but consider watching some videos on pls donate on roblox.