Kane can get definitely get more but one of the reason why they are such a great right now is cause he doesn't.
Another example is Detroit where guys like Lidstrom, Datysuk, Zetterberg, Rafalski have always got paid very well but never at the max they could have got.
I'd pay Kessel up to 7 per year for the full 8 years but if he wants Perry money at 8.625 per year then I'd shop him. It's already starting to look like Anahiem is going to be a weaker team from both Perry/Getzlaf trying to get max dollars which means they won't be able to afford Ryan much longer.
It comes down to a question of does Kessel want to be a winner or just make as much money as possible. If he just wants to make as much as possible then is he the guy to build around.
He'd be lucky to be considered a top 20 impact player in the league cause D, C and goalies can have that much more influence on a game. Top 20 or even Top 10 offensive player sure but guys like Chara, Weber, Doughty, Quick, Toews, Crosby, etc. have a bigger influence because of what else they bring.