Alcohol markup is actually the only thing restaurants really make any money on. We recently went to a pizza place in town that doesn't serve alcohol. I actually didn't know before going, or else we would not have gone! I was telling my mother in law about it because she is in the restaurant biz. Her reply was "wow, how they make money?"
My uncle received a commercial draft beer dispenser in payment for a job. Set it up at home and had it serviced by a local beer distributor. Using the cost of the beer, CO2, delivery and electricity to power the refrigerator, we figured the approximate cost for a 16oz mug was less than 10 cents per 16 oz mug. Bars and restaurants in my neighborhood get anywhere from $2 to $5 a mug for draft beer.