so first off im hesitant to agree that ROI=contract size/Superbowls...i think that needs more work
secondly- if your point is that signing bigger contracts (outside QB) limits your ability to improve the roster elsewhere the answer is yes, obviously. but singling out WR is pointless if you're trying to argue that it's not an important position. go look at the top 10 or 20 or whatever highest contracts at ANY of the important positions- LT, CB...not a lot of Super Bowl rings there either. that is because there are not a lot of Super Bowl rings to go around
what it doesn't mean is that you shouldn't invest at those positions