There are several factors at work here. First, is the inherent inflation of the MLB salary market. Every year their are shocking new deal which raise the average annual salary. While the AAS is not a perfect indicator of the market for upper echelon talent, I think it's a fair measuring stick because one could argue that the pre-arbitration players serve as a drag on the average and that the inflation of free agent deals (or deal which buy up free agent years) is actually MORE than the rate at which the AAS rises.
Second, there is the difficulty of perfectly discerning a players value based on comparisons to other players when no two players are exactly the same. Admittedly we can only approximate here.
Third is the "projectability" of any player. How will Wells, or any other player, age and what effect will that have on his market value.
So obviously there are enough uncertainties to make absolute decelerations impossible. Still, there is much we can learn. From the start, let's establish the comparables. If you look at the careers of Vernon Wells and Tori Hunter through the year in which they turned 30 (Wells turns 30 next month) you will find a very good comparison. Using OPS+ as a measure:
age - VW - TH
23 -- 96 -- 71
24 - 132 -- 80
25 - 105 - 101
26 - 104 - 124
27 - 129 -- 98
28 -- 85 - 104
29 - 121 - 106
Looking at that you HAVE to conclude Wells is a better hitter to that point in his career, and while his defense has slipped enough that fair minded people would agree it's not on Hunter's level anymore, he does enjoy a good reputation as a defender. Hunter went on to post a 112 and a 122 before his free agent year. That is to say the year he was a free agent he was essentially the exact same hitter Wells was in 2008. and had a lesser history with the bat.
Hunter signed a contract with an average annual value of $18 million, the same as Wells' AAV, by the way. Also the same as Suzuki's and roughly the same as Andruw Jones and one million more than Alphonso Soriano's. If you look at the last three years before the contract signing of each of those players you'll find they are pretty similar offensive forces, albeit with obvious differences in their strengths.
So I think we can say with some confidence that the market for a hitter of that caliber in the current market is an AAV of roughly $18 million.
As for the projectability and aging issue, Hunter signed a five year deal at about 32.5 years of age, Suzuki had just passed his 34th birthday, Jones was coming up on his 31st, and so was Soriano. Not to get ahead of myself, but just to get it on the table, Wells will turn 33 the winter of his option.
Now, with those parameters on the table, let's look at market inflation in baseball salaries.
Here's a chart of the growth in the average salary in MLB over the last seven years, and the precentage increase over the previous year:
(the original, going back to 1989, can be found here)
Now, let's average the annual inflation rate over those seven years. When you do that you get 4.9%. for the sake of simplicity, I'm going to round that up to 5% annually. (nine out of the last 13 years it has been higher than that).
Now, let's take a player who is "worth" (in the current market) $17 million annually beginning in 2008 and see where his salary goes if he stays with a market that's going up at a rate of 5% a year. In the first column is the year, in the second is his market value in that year (all other things being equal of course), in the third column is Wells contract value that year and in the fourth colum is Wells age:
'08 - $17.00 -- $9 - 29
'09 - $17.85 - $10 - 30
'10 - $18.74 - $21 - 31
'11 - $19.68 - $23 - 32
'12 - $20.66 - $21 - 33
'13 - $21.70 - $21 - 34
'14 - $22.78 - $21 - 35
'15 - $23.92
'16 - $25.12
I remind you that after the 2011 season, when Wells can opt out, he will be approximately 5 months older than Tori Hunter was when he signed his 5 year, $90 million deal. According to this math, if he had signed that deal in the winter of 2011, at the same place in the market adjusted for baseball inflation, it would have been worth $114 million (an AAV of $22.8 million).
So, what can we conclude from this information?
First, that the seven year deal, as it stands, is not in point of fact, over-market. On the contrary, a deal which starts in 2008 at $17 million and escalates at the same rate of the overal salary structure in MLB does would - over seven years - total over $138 million (Wells deal is worth $126 million).
Second, if Wells did opt out after 2011, the 4 years that the Jays actually would have gotten out of him would have cost them $63 million (AAV $15.75). Our "market value" for those four years is over $73 million (AAV over $18 million). In that scenario we still somewhat underpay.
Third, and again, all this assume Wells maintains his current level of productivity through at least 2011, when Wells gets ready to make his decision, he'd be looking at 3/$63 to stay, or the potential of a guarantee of $100 million or more over five seasons if he gets a contract that is market value.
So, simply put, if Wells remains a guy who is a 110 or better OPS+ player on average over the next three yerars, he will have a strong financial incentive to opt out and, short of Halladay-esque loyalty, will definitely do so. He could even afford to decline somewhat offensively over that time and the decision would still be tempting. Further, barring a decline to under 100, or a complete lack of ability to play CF by then, the Jays would not be overpaying if he did stay the full seven years (albeit, they may have enough depth that they sould still prefer to see him move on).
The obvious conclusion is that Wells' contract is not too high, but is in fact, at worst, fair market value in the current market.
Now, does that mean it was a good or smart deal? No, I don't think it was (and THAT is what makes it harder to move) for this reason: if you are going to guarantee over $100 million over the next seven years, you should be getting a player at a recognizable discount which offsets the built in risk that the player will decline in productivity. IF Wells continues at his current level of production for three more years, then the Jays signed a deal which paid off. If, on the other hand, he declines significantly, either with the bat or his defense becomes so bad he has to be moved out of CF in that time span, then the Jays are on the losing end of the deal. the point is, that the Jays have assumed ALL the risk and got no significant discount for doing so.
So it's not a "good" deal, but it is far from an overpayment either.