If you're truly looking at the contracts in that way then yes it doesn't make sense, but that's more because looking only at the new years of one and the total years of the other doesn't make sense. Mayo's contract: signed him through his prime years, allowed the Pats to finagle cap hits, and payed him fair value. There's really nothing about it that makes it an outlier.
IMO the problem with the WW situation is that there isn't a lot of room between the franchise money/years and fair money/years.
If you look back at all the other early deals they did (Light, Koppen, Warren, Brady) it is an outlier because none of them ever approached top of the market new money in early extensions - although Koppen's was top 5 before factoring in the remaining rookie year. That used to be the rule for landing one here, you didn't land in the top 3 let alone set a new bar. Seymour did, but then he only got 3 years at that money and after factoring in his remaining rookie year he didn't as that lowered his average by $2M. And with the exception of Brady's second extension and Warren's, they were in in their final season, often a month or more into it.
Brady's second deal in the spring of his final year on his rookie deal after he'd been the SB MVP was for $6M per in new money. Rookie #1 draft QB Alex Smith's contract AAV that year was $8M. In 2005 after the third championship when Brady got $10M per in new money that then put him in Eli Manning's range, but $3M per behind Eli's older brothers 2004 deal...
When Branch left it was over being offered $4M times 5 in new money less having to play out the final rookie deal year. Seattle gave him $7M times 6 after the trade.
They fought with Mankins when he wanted top of the market $7M+ in new money. They made him wait til his rookie deal was up and then RFA'd him and offered $7M per in new money plus one year at $3M that would lower the AAV to $6.5. That's why he held out. And for him it worked since he ended up a year later getting top of the market $8.5M per in new money...thru age 33. Ordway kept pointing to his holding out yesterday as a smart strategy but claiming he never made back the lost money from that holdout season. Wrong. He got $2M more over the next 6 so he's made it back and more. Whether he makes it through the whole 6 years or not he made out, too, since he got $30M guaranteed and they were only offering $25M on the earlier deal.
Brady finally topped the market, briefly before Peyton matched him, in his last deal. But only in new money because again there was that one year remaining on the old deal.
There just isn't a lot of rhyme or reason to it anymore. I know they don't have a lot of room between what Welker wants and the tag, but remember - the tag isn't what it used to be. The average of the top 5 WR's in 2011 was $11.5M. Only the tag formula just changed to the point it isn't top 5 money anymore - it's $2M less. It probably isn't even top 10. And back in the day they were always up against the cap, not the case now as with Welker under the tag they are $14M (more than 10%) under. Why they restructured Brady is anyone's guess because that money will either go to an extensions later this year or have to be rolled over into 2013 when we are already again well under even a flat cap.
And again, it's not like Welker is 33, he's 31 so he has three seasons to even get there. They could easily structure a 4 year deal at $8M per that would be cap friendly now and in the future by frontloading all of the guaranteed money in year 1 and 2 salary requiring only a modest signing bonus giving them flexibility on the backend including to cut him or his salary with little dead cap consequence in the final season or even sooner.
My new theory is maybe Rap is on to something and they are afraid of him becoming another Wayne Chrebet. But Chrebet, who never remotely approached Welker's production, had a long history of concussions ignored which led to him hitting the wall early. So unless there is something going on with Welker that we've never been apprised of via injury report... I just don't get it.
The Troy Brown comp is ridiculous IMO. Troy was never the same after he injured his knee, and it wasn't even an ACL - which Wes already rebounded from. Browns was more cumulative wear and tear that forced surgery 11 seasons into his career at age 32 from which he never fully rebounded. He lost his remarkable first step entirely at 33, and that first step was the centerpiece of his game. Wes won't even be 33 for 3 more seasons...and he's only got 8 seasons on his knees at this point. I've seen a few pundits raise the issue of the ACL history, but nowadays a repaired ACL once rehabbed successfully is stronger than a non repaired one. A receiver like Colston with multiple micro fractures on both knees, that's a different equation. And he just got a 5 year $40M extension with $19M guaranteed...at 29.