It is a frightening thought though to think — am I more conservative than my parents?
Freemium games make sure there's enough "there" there to keep casuals almost happy. The trick is to make the $5 and $10 premium purchases let you do around 4-12 hours of gameplay advancement, but that's it. Consider something like Shop heroes (or whatever) where you can put thousands of hours into the game for free, a day or two "skip" for $10 isn't a good value proposition. But skipping a week or a month? maybe after someone has put $10 in a few or several times and gotten that little jolt they want to feel the big jolt of a lot of money.
I know i spent around $100 in the blizzard RMAH (Real Money Auction House) on diablo III and it netted me nothing - nothing at all. So i learned my lesson real quick. Real money for virtual goods is a non-starter.
Now as far as robux goes, I want my child to understand that it's ok to pay people for their work (designing the levels, making items/skins). So he can choose to spend his money on hotwheels, paints, robux, google giftcards, whatever, $5 at a time. I do sometimes make a frowny face when he chooses robux, though; because as i said, a billion dollars!