It seems that the Yankees are willing to pay more per value-added than any other team in baseball. The Red Sox pay a lot per win too, but not as much as the Yankees.
I think all teams set their value for these wins and refuse to budge beyond it. Players like CC, Teixeira and A-Rod all break the bank but they are worth it, for the Yankees, at that cost. For some reason, a player like Carlos Beltran was not worth it for the Yankees, but he's really the only player I can think of whose cost has appeared prohibitive for them. Matt Holliday might also fit into that category, as he was the best available OF in a year when the Yankees needed an OF, and they didn't touch him.
A comparable signing for the Red Sox is someone like JD Drew, whose contract dwarfed anything else being offered to him and has many wondering if he is worth it. I'm pretty confident that he is worth it to this team, but wouldn't be worth the same salary for, say, Houston or Oakland.