It's a value trade-off. If you were to go to one game, you're looking at that price for 2 tickets, maybe even only one.
The cost of each game (@4 games/month), if that is the only thing that you watch during the whole month (not baseball playoffs, NBA, shows, Sportscenter, news, anything), is $18.75 a game.
That's three trips a month to donate plasma.
Other option: Go to a sports bar and buy a soda.