I think this needs a little more context. What are you referring to as "an average night out"? Drinking, or different activities that we do regularly?
If by drinking, I'm not much of a drinker. Rarely drink at home, and will limit myself to two beers in a social setting as one of my jobs mandates that I not have any kind of alcohol infractions. For me, a two beer tab with tip will be around $20-25USD depending on the high end. If I'm drinking a couple of Miller Lites, it can be $5USD.
As to other activities which constitute as "an average night out". Costs vary greatly depending upon the activity. Free on the low end for a bike ride with friends, to $250USD depending upon what the activity is.
Lately though, my "average night out" of the house has me earning money.