Oh, I think you're over-interpreting. What's actually going on is that the Yankees have just spent an extraordinary amount of money on a stadium, and need to make good on their investment. They thought that would be easy - the stadium was planned and built at the height of the bubble, as Wall Street was awash with cash. Now, Steinbrenner's feeling intense pressure from those who've already locked in their seats, and even more pressure to move the many seats and boxes that are still available. It's not enough just to be the Yankees; to service his debt, he's got to put some real entertainment value on the field.
So the marginal utility to the Red Sox of signing Texeira? Relatively small. You can't sell more seats when you're already sold out for every game, and the broadcast revenues are more of a longterm proposition. The marginal value to the Yankees? Immense. He can help fill a park they desperately need to sell. That's why the Yankees are setting spending records - they can actually generate a return on their investment. Indeed, they need to.
On a wholly tangential note: What're the ethics of the NYT copying a story from their Boston subsidiary? (In this case, the Cavanagh Company and its wafers.) There's no newshook - it's just a fascinating feature that ran in the Globe at the end of November, and which the Times has just replicated today. Wouldn't they have been better off simply running the Globe story in the Times?