The other day The Hardball Times wrote that Alfonso Soriano is not overpaid. I'm a big fan of anyone who doesn't talk about Soriano in a way that makes him seem like he's a lazy, overpaid player. However, THT relied on fWAR, which uses UZR as its defensive metric. His 2007 UZR is so high that my iPad probably won't let me type it out. It's ridiculous to think his defense was that valuable just as it's ridiculous to think that Darwin Barney's DRS this season is in any way realistic. It isn't and it wasn't for Soriano either.
fWAR has Alfonso Soriano being worth 18.7 wins since he signed his 8-year contract. On the other hand, Baseball Prospectus' version, WARP, has him at only 12.3. Baseball Reference's version, what we usually call rWAR, has him at just 5.8.
By using fWAR, The Hardball Times reached the right conclusion, but if we use either of the other versions it's not even close to true. BPro's WARP is right in the middle of the other two and if you averaged the three you get just over 12 WAR. That's over 6 WAR less than what Fangraphs has and if we ran the numbers again we'd find that he is most definitely overpaid.
I'm not sure we should really be saying overpaid though. Yes, relative to what he's produced for the Cubs he has earned more money than you'd like, but that's not how contracts work. The team that signs the player is most often the team that bid the most. In other words, no other team considered an offer so high. Because of that, it's safe to say that in all such situations the team that signed the player overpaid. If you're willing to pay something that no one else is, it's very likely you have overestimated the value of that player.