In theory, Bourn should get a number somewhere between Pagan's 4/40 and Swisher's 4/56 deal.
unfortunately for the Mets, Pagan is vastly overpaid, imo, and Swisher is minimally overpaid. Based on these two contracts it will be really tough to give him less than 4 yrs.
It'll come down to whether there's another team involved. If there's no market for him, Sandy should be able to keep to 45. He probably has a number in his head already and if another team forces him beyond it, he'll walk away.