This isn't entirely fair. Who drives to a Yankees game or a Red Sox game? Sane people take public transit. You should factor in "cost of [most common] transit to the game."
(And this is coming from someone who is in one of the least expensive towns.)
That's a fair criticism. I don't have data on common modes of transit to games, unfortunately. I can assume that it's high for big cities but there is no way for me to know for sure. If I run across that data, I'll for sure revisit this.