He gets a lot more money from sponsors if he moves to a big market team. I think the pay raise from the sponsor is so substantial (I've heard upto 60 mill from someone, not sure if true) that the Cav's ability of being able to offer that little more money or an extra year might not matter too much to him. The decision for him is if he wants to stay to keep playin for the homtown team or bolt to a team like the Lakers/Knicks and become the poster child for the NBA/Corporate America.
That's why I think a Cavs/Laker trade makes most sense. Kincks don't have anything to offer. Lakers can almost give back most and be assured that they'll be able to keep the guy they just traded for beyond his contract.
Lebron has Laker written all over him. Those bastards always end up getting all the HOFers because of the city.