How much is Darwin Barney worth in a trade?

Before we look into Darwin Barney's trade value, I was thinking I wouldn't be that confident in the numbers below. Most of the time I am, but for someone like Barney I'm not. At all. Why? Because of Placido Polanco. To understand why you can check these two links out. IN the first link written after the 2006 seaosn, Tangotiger takes a brief look at Polanco and Derek Jeter and finds that Polanco is as valuable as Jeter, but costs significantly less. In the second link written in 2011 he looks back since 2007 and finds that they have essentially been the same player in terms of WAR. The difference, however, is that Jeter made a crapload of money and Polanco did not. 

Polanco has only had a few seasons in his career in which he's been better than average at the plate. He's known for his defense. It's what continues to allow him to be a productive player. He's only earned $42 million in his career. He's been underpaid throughout his career. 

One thing in Barney's favor is that he still has 4 years of club control following this season so he does have value, but it won't be as high as the numbers will suggest. 

ZiPS projects an additional .5 WAR from Barney the rest of the way. PECOTA has him at .6 and Oliver, if we add in 4 runs of defense is at .5. The average is .5 over half a season so a full season is 1 WAR. He's still in his prime so there's no reason to think he can't maintain that for a couple more years. 

2012: .5
2013: 1
2014: 1
2015: .7
2016: .5

The total is 3.8 WAR. As you can see, while Barney is good defensively, he's no Polanco and he's not close to Polanco at the plate. Let's say there's an average win value of $6 million over these years, that makes Barney worth just under $24 million. I've put together a salary estimate for Barney over these years.

2012: .4
2013: .4
2014: 1
2015: 2
2016: 3

That's just a quick guess. Someone who is as valuable as Barney is won't be paid a lot of money so that seems reasonable to me. It's a total of $6.8 million or  actually $6.6 million remaining. The estimates could be wrong. I don't think so, but I also don't know. That leaves Barney with quite a bit of surplus trade value (about $17 million). 

I'd say the Cubs could get a pretty good prospect for him, but  I just don't see any team giving up a quality prospect for someone like Barney. Much of Barney's value is his defense and I'm not sure teams are going to buy that kind of talent for the market rate. I'd probably cut that number in half and go with $8 million and say it's good enough.