The Florida Marlins are closing the upper deck to their stadium, which will get rid of a large number of cheap seats. The Oakland A's did this a few years ago too. Yet even when the A's have games where the stadium is sold out they don't open backup the upper deck (example the mid June series with the Giants).
I have been thinking about the issue of stadium size and attendance recently for a paper I'm working on. By making a smaller stadium, the Marlin and A's lower costs. They also get rid of cheaper tickets, so although they may sell fewer tickets they may make more money if some people buy more expensive seats.
A potentially related paper from Nobel prize winner Gary Becker, written in 1991 in the Journal of Political Economy. He proposed that some restaurants might not raise prices even when they are full and have long lines. The basic theory is that the demand for a good may be tied to the perceived popularity.
I haven't fully made the connection between Becker and the closing of upper decks, since the Marlins aren't like the popular seafood restaurant in Palo Alto Becker describes with lines out the door. However, the enjoyment of going to a game may be linked to how full the stadium is and how the team is perceived to be just like how I perceive a restaurant might be related to how crowded it is.
h/t to the International Journal of Sports Finance