Watkins makes others on the team better by drawing the other team's top cover guy, drawing double coverage, and/or taking the top off the defense.
Woods benefits from Watkins' presence. So do Kupp, Gurley, et al. Watkins should not only be paid for what he personally produces in catches/yards/TDs but should also be paid for the benefit the other guys reap from Watkins' presence.
How many catches/yards/TDs would everyone else have if Josh Reynolds had gotten all of Watkins' snaps? How many yards would Gurley have if Watkins was never on the field? Hard to quantify but the easy answer is 'less'.
That being said I have no idea how to convert all of Watkins' value to dollars. Hopefully Snead and Watkins' agent can figure it out.
AlbaNY_Ram