We can make the best sane offer in the world. If the Yankees want the player enough, they will counter with an insane offer. (see Rodriguez, Alex). Simply put at some point we reach the level where we still need to try and be at least somewhat fiscally responsible for the benefit of the long term health of the franchise. For all realistic purposes the Yankees really don't.
You think the presence if a 19 year old kid with defensive questions at catcher will stop them from acquiring the best available player at the position? Heck, would it stop us?
Besides, Montero can back Mauer up.