The thing about it is if you lose your long snapper in a game, you don't have a guy who's gonna do his job successfully 199 of 200 there. you got a guy who may have done this for a year or two in college 7 years ago, or a guy who showed it off a couple times in camp fooling around. Now every punt is a potential disaster on top of field goals. Even a 21 year old veteran longsnapper coming into a different situation can cause problems right? just ask the 2002 NYG. And he was their 4th replacement.
Also, if long snappers were so bountiful, I doubt they would keep Mannelly @~1Mil opposed to a younger guy at the minimum for half that.