In cases of top players the agents know what the number should be based on the market and ask for that. Burrow took 275 (little more than the guy before him), he didn't hold out for 350.
I'm sure Ja'Marr is not asking for 50 a year and 250 guaranteed. His agent is likely using Jefferson's deal and asking for a little more than that.
As for Watson, he's not an all-pro HoF player like Ja'Marr is.