The deal is supposedly worth $66 million dollars over 4 years, with a vesting option in 2014 for $14 million or more. Depending on the stipulations of the vesting option, that could basically mean that Bay got the 5th year he was looking for.
Because the Mets are in the top-15 picks of the draft, the Red Sox will only receive their 2nd round pick to go with the supplemental pick. At the moment, this leaves the Red Sox with 2 supplemental picks added on to a standard draft, having lost a 1st and 2nd rounder to the signings of John Lackey and Marco Scutaro, and gained a 1st and 2nd rounder from the loss of Billy Wagner and Jason Bay.
Though Jason Bay was popular in his relatively short tenure in Boston, there were concerns about his defense, and how well his offense would last as he aged. Though in recent days there had been rumors of renewed interest in Bay from the team, it seems unlikely that they ever offered more than the 4 years and 60 million dollars they offered Bay earlier in the year.