Centurylink Arena in Boise, Idaho, sells beer in two sizes.  A $4 small and a $7 large.  The $4 small gives you 16 ounces of beer in a plastic cup.  The $7 large gives you... 16 ounces of beer in a slightly taller cup:

 Two fans got hip to the scam and made this video, which went viral.  The arena has apologized and called it a mistake.  OF COURSE IT WAS!