Kevin Brown, Carl Pavano, Randy Johnson just to name the most recent.
You imply that they acquired these guys because they cost a lot, not because of their talent levels.
In '03, the Yankees had just lost Clemens and Pettitte. Brown had just posted a 2.39 ERA with 185k in 32 games started.
In '05 the Yankees acquired Randy Johnson after he had posted a 2.60 ERA with 290K and 44 BB
Carl Pavano was the most highly coveted pitcher of his FA class, had many clubs make him offers, and actually took less money than the Red Sox offered him to pitch for the Yankees.
So it's not their M.O. to acquire the highest priced talent, but the best, which generally costs more.