I definitely agree that he hasn't reached his ceiling.
The problem is, he's never reached his ceiling on any team, and I don't see a lot of evidence or reason that this will motivate him to actually do that.
But even if he doesn't reach his ceiling and only does what he did last year, the contract is about right. And he's the only player we have that can win one on one in a pass rushing rep. The rest are just guys that can occasionally get a sack if the QB holds the ball to long or pressure is schemed.
He's basically a 7-9 sack guy which is pretty much so worth what he is being paid. The double digit sack guys are getting double what he got and more for the elite guys. If he improves over last year, we got a deal, and if he ever does reach his potential, we are robbing him with this contract.