Nate Silver has an excellent piece on player turnover on ESPN.com. He points out that due to free agency (and baseball wealth) that turnover among veteran players is higher than it's ever been:

What has caused the high rate of player turnover in the Selig Era? Most of the period has been characterized by rapid economic growth, both of the Alan Greenspan boom economy in general and of baseball revenues in particular. In a market as dependent on local sources of income as is baseball, a greater surplus of wealth can very easily create greater differentiation in the ability to generate marginal revenue, especially when accentuated by profound differences in front office smarts. Jason Giambi is worth more in New York than he is in Kansas City, and the gap is greater than it was in the early days of free agency.

And so, Selig and his cronies have it half right; although recent seasons have been characterized by high turnover of veteran players, these conditions have arisen not out of any economic struggle, but out of baseball's abundance of wealth.