I think the idea that a guy will play for quite a bit less for an opportunity to win a ring, is imaginary.
Maybe a slight bit less, or maybe if the structure is slightly less favorable. But, no player is going to play for $8 mil if market is $10 mil. $2mil is a lot of money even to a rich person.
I can't imagine the Rams paying a RB more than a couple of million. Williams is too darn good to turn around and hire a RB 1b at a substantial number. Besides, potentially impactful RBs can be found in pretty much any round. The colleges, even Div III, are putting out some pretty amazing kids.