Worth it is a relative value. Many people thought the Rams overpaid for Stafford. How much a SB ring is worth depends upon the individual. If Cleveland wins a SB with Watson as QB then the ownership will reap a $$ windfall far greater than the money spent on Watson in terms of ticket and gear sales for years. If they don't they look like fools.
The only problem I have is how much it will affect their effort to build and keep a team around him. We have seen how that success makes it harder to keep FAs who now have a ring and want to cash in on it. IMO teams need to have the talent already on the roster and really only need the QB and perhaps one or two other players. Had Woods and Akers stayed healthy IMO they would not have needed OBJ and Michel and they still would have won that SB ring. Stafford and Miller would then have been the keys to winning.
I'm not convinced that the Browns were simply a QB away from a SB ring. They got rid of OBJ and Landry, and sure they signed Cooper but who else to catch those passes? The Rams already had Woods, Kupp, and Jefferson, three good WRs. The Browns have Chubb at RB and a decent defense expected to rank about 13th but if they expect to draft an elite WR in this draft that's assuming a lot. Without elite WRs a top-tier QB is meaningless. That's why at this moment I see a team that could contend to make the playoffs as a wildcard but they are in the same division as the Bengals. Watson alone doesn't IMO put them over the top. The Bengals had Burrows and it still wasn't enough.
The Brown will need to do more if they want to contend for a division title much less a SB.