The Yankees spend the money because they can. Both the Yankees and the Red Sox operate at a small loss, compared to teams like the Marlins who take in all the money they can from revenue sharing and just pump it into the corporation instead of putting it back into the team.
These teams have national recognition not only because they've been around for over 100 years apiece, but because they invest right back into the team to keep themselves on top. Look at the Mets, or even the fucking Rays, who have none of the glitz and glamor of the Yanks or Sox, but they spend the money they make and as a result do well and see an increase in revenue year after year, spending that extra money on better players so that they can do even better in the coming years. The Marlins on the other hand get young players, pick up free agents on the cheap, and dump them at the end of the year to turn a profit. I don't see this hot streak they're on continuing for long, but we'll see how it goes, maybe I'll be wrong.