I seldom buy merch, save for the occasional CD, usually a replacement for something I "borrowed" off the internet (the artists make the most money off their product if I do it that way). I used to buy a poster or two as well, but the Fillmore gives them away so I don't have to buy them any longer.
I'm good for about two drinks a show, usually a bottle of the High Life. I've pretty much given up the hard alcohol over the past few years after a few "unfortunate" incidents. Sometimes, with permission, Whiskey Vansmack gets to make an appearance, depending on the artist.
So, on the average, just about $11, $20 if I buy a CD. And I rarely drive to shows, thus saving gas and our environment.