I think this will come if he knows he's number one choice. As I said, he probably doesn't want to make a hash of coming for a ball and missing so stays back and does what he currently does best and that's stop shots. Kicking and taking high balls can be coached, reflexes and shot stopping not so much.
I would probably say about that for me too, maybe even 5m. If that money was invested back into the squad it could do wonders. Saying that, I would prefer to not sell. I would love for him to become a town legend along side Tommy and Hewitt, you can't really put a price on that.