It´s not the best judgement of value but it´s close to guaranteed that he would have signed somewhere else if the Packers didn´t offer him $10 million a season.
Is he worth the same contract as Jordy Nelson? Take away Randall Cobb and Jordy Nelson still plays like a number one receiver. Take away Aaron Rodgers and Jordy still makes big plays even with badly thrown balls. Can the same be said for Randall? I'm sure he would have signed somewhere else, and if that team didn't have the right kind of talent he'd be on the hot seat right now as an overpaid FA acquisition.
He's not just a system guy, but he needs a certain level of talent around him for him to play at his best. I'd rather pay Cobb type money to a guy who really could be the number 1 if needed and who really could replace Jordy Nelson down the road.