This has to be one of the most interesting or perhaps infamous deals in sports history. The Mets actually thought that they were entering into a profitable deal due to their association with Bernie Madoff. The Mets' owners, the Wilpons, had accounts with Madoff that they thought were earning 10% or more per year. With the 8% that they were paying on the Bonilla deal they had a profit, right> WRONG! More at the link.
http://www.espn.com/mlb/story/_/id/1...ry-july-1-2035
Another interesting deal, albeit on a much larger scale, was the one that the Silna brothers made with the NBA. They torched the league for many millions of dollars in what has been referred to as the greatest deal in the history of sports.
http://hangtime.blogs.nba.com/2014/0...f-aba-spirits/