Even though I don't necessarily agree with Wins Produced (common complaints are that it overvalues rebounding and undervalues shot creation), The Wages of Win is one of my favorite sports blogs.
One recent post evaluates players based on how many wins they theoretically added to the team and how much they cost.
Players with a positive net value (produced more in value of wins than salary paid): Rondo, Pierce, Allen, Garnett, Daniels, Shaq, Delonte West, Troy Murphy. (They have Daniels and Murpy at zero salary. They give Daniels a value of wins higher than his salary. They give Murphy a mild positive value of wins, but lower than his pro-rated salary)
Players with a negative net value who produced a positive value of wins (but not as much as their salary): Chris Johnson, Von Wafer, Carlos Arroyo, Kendrick Perkins, Nenad Krstic, Jeff Green
Players with a negative wins produced: Sasha Pavlovic, Luke Harangody, Semih Erden, Avery Bradley, Nate Robinson, Glen Davis, Jermaine O'Neal
Basically, the Big Four produced most of the value, exceeding the value of their contracts, while Nate Robinson, Glen Davis, and Jermaine O'Neal were the huge sinks of dollars for not much in return.
Rondo was the 15th most underpaid player on list mainly made up of players on rookie-scale contracts and stars on max (or near-max) contracts who contribute more value than the max contract.
Jermaine O'Neal was the 30th most overpaid player, but the overpaid list is typically dominated by injured players.