A car is the only thing beyond basic survival that I have spent any real money on, and even that only recently (first new car 2014, under $15k total). Before I always got super cheap used cars and keep them for decades, but the government did that crush all used cars thing and destroyed the market. I've never really spent much on my PCs, usually getting parts as gifts or hand downs. Probably less than $10/month on average.
Which means that beside my car, the most expensive thing I've splurged on is food. Sometimes I just can't resist eating real food, and I'll actually buy stuff at the store...or every few months even go to a restaurant with a friend/family and spend up to $15. I know it averages more than $10/month, this month I already spent $20 on food.