An evening out with my better half:
Movie: $30 (With popcorn and sodas)
Dinner: $30
Ice Cream: $15 (Coldstone, the good stuff)

$75 minimum. Pretty close, depending on where you go to eat.

If I take the kids, $100 won't even come close.

Considering how most WoW players have failed to mate within the confines of their mother's basement, the $75 is probably closer to the mark.

You could get by cheaper without the movie snacks, eating at McDonalds, and buying a tub of Ben and Jerry's for dessert but, again, that reduces your mating opportunities. You'd still be down for more than twice your monthly game sub for only a few hours of entertainment.

All in all, $15 a month for a MMO sub isn't a lot considering the number of hours you get out of it per month in entertainment. According to my calculations, based on my play time, I'm averaging $0.19 per hour in costs. Not too shabby when you're paying around $4 an hour for a movie.