If you look at an average middle-class family you'll see that having about $1000/month of cushion after taxes and bills is considered an uncomfortably small amount. You'd rather have more so that you can save more for retirement or it wouldn't be a big deal to buy a car, etc. That being said, $50 or $100 per months on top of your normal entertainment budget is actually very little -- going out to dinner as a family will cost you over $100 at any decent restaurant. Doing anything will cost a lot more.
If you are employed in your twenties, and you have no family, you may have tons of disposable income (maybe $2k/month or $3k/month) to do whatever you want with after your bills and rent. Games are a very cheap form of entertainment compared to many other hobbies.
