If he can be a legit and consistent third option, inside a good offense, then let him prove it and pay him the money. There's no way in hell I'd extend him at the upper range given here -- the only corner in the world that views Burks as worth more than maybe $8-9mm (not even SB nation voters thought that).
So far he's shown the offense cannot go through him and he requires someone to create for him. I see third options more like Barbosa, Ginobili, Kevin Martin, etc. Someone who can create with all the pressure and focus still on them. Is Burks that guy? Will he become that guy?
BTW, I'm predicting his 3pt% and improved defense this season earns him an extra million or two. He's not the 36% 3 point shooter his stat says he is, but can he do better in a more airy system?