Clearly TruJ and/or his agents have severely overestimated his value (not unusual in pro sports).
I think he is a valuable member of the Rams. But in no way is he a member of the elite group of CBs in the league. He is a B+ CB, which is very good. I don't ever see him loafing; you don't ever hear of a bad attitude; no issues off field that I'm aware of. But he nowhere near a shut down corner.
If he wants the elite level contract money he won't get it in LA. Partly because he's not worth it and partly because the Rams have other, just as valuable if not more valuable players to re-sign. And I think Joyner is more valuable to the Rams than TruJ because he can play virtually every position in the secondary.