http://www.nytimes.com/2012/10/15/sports/baseball/attendance-down-for-yankees.html
On a sunny afternoon, 47,082 fans were at the stadium to watch the Yankees play Detroit in Game 2 of their best-of-seven American League Championship Series. It was the third straight playoff home game that the Yankees drew fewer than 47,200 fans, or about 3,000 short of capacity. During the previous 17 playoff home games dating to 2009, when the new Yankee Stadium opened, the Yankees averaged 50,140 fans.
WOW. I was gonna call BS, but it's a reliable source in the NYT. And I saw this. I would've NEVER thought the Yankees would not sell out a playoff game....and baseball playoff games in general aren't even ridculously overpriced. But maybe the Yankees games are, I dunno...
Ushers were told to move fans in the upper deck into empty seats below so the unfilled sections would be less noticeable, according to Yahoo Sports.