I think for what he brings, he's worth that to THIS team. He's scored at a consistent 55-60 pace for the past several years, and while some say he's slowed down a step, I also think he's been able to introduce some more skill to his game.
But what's just as important is what he does when he's in a slump. He brings energy, he brings physical play, and if SOMEBODY needs to make a statement, to play themselves to death, he's the first to do it.
Ryan Callahan plays in every situation, and in recent years, has excelled in every situation, relative to his role on the team. There are some who expect him to be a 1st line scoring superstar, or a 3rd line grinder. He's neither. He's a 2nd liner who provides BORDERLINE primary scoring, but specializes in fore-checking and defense.
Is Ryan Callahan worth 6M to say, St. Louis? No. They have players like him. They have a wealth of players like him, actually. Would Ryan Callahan be worth 6 million to the Rangers if they had more players like Dubinsky, Backes, Brown, Landeskog, ROR, Wheeler, Oshie (you see where I'm going.)? No.
The Rangers have 2 forwards who bring that type of fire. Callahan, and amazingly, Zucc. I'd hope Hags would, but he hasn't. Kreider shows flashes, but nothing that sets a tone. You trade Callahan, and who's setting that tone? Stepan? Nash? Sure, McD, Girardi, and Staal all play that way, but I think you need a forward to set the pace, and the example, considering how involved they are up front.
I think for the offense, defense, leadership, physicality, experience, and effort that he brings, as well as what he means to that locker room (which we've seen to be, quite a bit), I think Ryan Callahan is worth between 6 million dollars and 6.3 million dollars per year to the New York Rangers, under the projected salary cap.