How is the price of beer determined at a bar?

Checking my Twitter feed I noticed someone had posed a curious question.  A question I had never really considered . . . how is the price of beer determined at a bar?

So, I did some poking around.  It turns out that the pricing is pretty much arbitrary.  As best as I can determine, it's whatever the bar owner wants to charge.  Its mostly like determined on what they think the patrons are willing to pay.

For example, there is a sports bar in Washington D.C. that discounts some of the beer on their menu according to a pro batter's average on a given day.  For example, if his average is .212 then the beer will cost $2.12 for the beer selected for this special.  Mind you, the beer usually chosen for this discounted price are stuff like Pabst Blue Ribbon and Miller Light.

Hubby and I go to the same bar every week for hot wings and cold beer.  Typically, we start out with by sharing a pitcher of, dare I say, Bud Light (hey, one must drink water sometimes, right?).  And then finish off with one of the craft brews on their rotating tap (kind of like having dessert).  I can pay as much or more for a pint or less of that craft beer - say Dogfish Head Olde School or Lagunitas Sucks - as I do for a whole pitcher of that watered down macro brew.  

However, I am willing to pay that price just to try a new-to-me beer or to try a beer I've already have to see how it tastes on tap as opposed to the bottle.  Heck, I've paid $9 for a 4 ounce glass of 120 Minute just to see how it tastes on tap.

Now, if I or any other customer refused to pay such stupid prices for a beer then it certainly would be stupid of the barkeep to charge those prices if his clientele wouldn't pay it.