Who knows what he'll want or get. I don't think there are players that don't overvalue themselves due to their aggressive agents.
In the end these things tend to be stats driven, position driven, and also driven by market scarcity.
Stats wise, Watkins is 58th among all WRs in receiving yards. 36 catches and 530 yards in 14 games.
So the question is, in a healthy season for him can these kinds of stats help convince another team that Watkins belongs in the talk as an elite #1 WR that makes $12 -14 mil per year? All it takes is one GM to think so. Look how it was with TA and the Rams.
However, lets say he finishes the year with 700 yards. Considering he is on a good team, with a very good QB, and a super bright Offensive mind in McVay, would a GM be able to convince ownership that Watkins is worth elite receiver money? I seriously doubt it. Andy the Rams won't go Franchise Tag because you're looking somewhere in the $16.5 mil range.
That said, the Rams gave up quite a bit to get him and will be anxious to resign him. My guess is that the Rams will let Watkins hit the open market to test the waters, letting him know that the Rams want him back. And, they'll more or less match the top offer unless they find it way too much.
Watkins will have to decide if he wants max wins or max money. I doubt he can get max money with the Rams because the ball is going to keep getting spread around so much in the Rams offense that it will be hard for any Receiver to get enough targets to put up the big numbers.
There's only room for one "the man" on the Rams and until further notice that man is Gurley.
Because of his young age, I'd think a good compromise would be a 2 year deal at $18 mil with the first year fully guaranteed. This way Watkins gets paid well and he can get another chance to put up better numbers after having an off season with the team to get fully familiar with the playbook and in sync with Goff. If he puts up big numbers, then he has a good chance at an elite level contract in 2020....he'd only be 27. And the Rams will have a year or two to develop Reynolds and Thomas to see if either can be that take the top off the defense threat that is needed in McVay's offense at a far cheaper price.