A few things to consider. Running back isn’t a highly valued position in Payton’s offense. Payton changes them out and uses them according to their skill set. If Alvin goes, Payton will find another one to replace him with roughly the same skill set. Maybe not ideally, but within a set of ability.
When has Payton given money to a running back? Hardly ever. Running back in the NFL is a disposable position.
Now, specific to Kamara. Ever since his first half year people were crowing for Alvin to be the next 300+ carry RB and take over for Ingram, no matter the fact that anytime Kamara gets a heavy load he gets banged up. He hasn’t managed to be the man yet. He also has damage to his knee which I assume is cartilage damage. Not good for a running back, certainly not one who has been knocked up as much as he has.
Not saying he’s not valuable. What I’m saying is for him to be paid as a top tier running back and get Gurley money means that either Lattimore or someone like Ramczyk won’t be able to be signed. You win long term with line strength, QB and CB play. Not RB play.