Dan Haren was acquired this year by the Miami Marlins to take a place in the rotation without investment from the club. Haren came free of charge from the Los Angeles Dodgers, who used their significant coffers to extract more trade value from an ugly Andrew Heaney trade. While the Dodger turned Heaney into Howie Kendrick and got four other interesting players to add to their envious depth, MIami got a successful (but now struggling) Dee Gordon and a free year of Haren.
That free year has overachieved expectations, depending on what numbers you look at.