I read that he's asking for high wages (€3m net, currently €1.4m net I think) for the renewal. a 4 year renewal would decrease amortisation expense by around €2.75m, but if his gross wages per year increase by that amount, then Juve would have nothing to gain from this renewal other than the option to sell him.
from twitter: Giovinco asks for €3M/season until 2018. [GdS]