Earlier today, Forbes published its "The Business of Baseball 2012" special:
"The average Major League Baseball team rose 16% in value during the past year, to an all-time high of $605 million. In 2011, revenue (net of payments to cover stadium debt) for the league’s 30 teams climbed to an average of $212 million, a 3.4% gain over the previous season. But operating income (in the sense of earnings before non-cash charges and interest expenses) fell 13%, to an average of $14 million in part due to a 5.1% increase in player costs (including benefits and signing bonuses for amateurs), to $3.5 billion in 2011."
Included is a list of values for all 30 MLB teams, with information on revenue, operating income, one-year value change, et al. The New York Yankees, unsurprisingly, came in at first, at a total value of $1.85 billion. Behind them, in order, are the Dodgers, Red Sox, Cubs, and Phillies. The Oakland Athletics, at $321M, have the lowest current value.