Just went through and looked at the #3 scorers on each team (looking at end-of-season rosters). 20 of 30 #3 scorers are not on rookie scale contracts. The average salary of these players this season was $10.6mm (using Boozer, not DJ Augustin, as Chicago's #3 scorer). A couple of these players also serve key defensive roles: Marc Gasol and Serge Ibaka. A bunch are considered terrible contracts: Bargnani, Carlos, David Lee, Rudy Gay, Eric Gordon (Deron, Deng, Bosh?).
The average salary of all 30 #3 scorers this season was $7.9mm.
Paying a player who is neither an offensive hub nor a defensive stopper $12mm+ per season is not smart.
You didn't take into account the natural rise in salaries from when they received their contracts until now. If $10.6 mill is the average for #3's not on rookie contracts, then a bit higher than that may still be an OK value. And even though Hayward lacks defensive stopping ability he does have some playmaking ability which adds to his value.
That being said, I'm really hoping the Jazz sign him for $10 mill or less.