If I had the power to make decisions in WWE and was tasked with bringing in Sting, I'd do it in the following ways...
Rather than pitching money towards Sting, I'd wait for the opportunity to insert him into a storyline along the lines of what he is used to as a character. I'd explain to him that while he will be given a main event push from the outset, that he will be expected to put others over (mainly the up and coming talent). In order to solve his reluctance to this I'd explain that such losses would be at PPV events and would be in competitive contests that would highlight both participants strengths.
If he agreed to that I'd then offer him a 1 year performers contract with a 3 year Legends Contract (to keep Vince happy and make the most out of merchandise sales). I'd offer him the very same light schedule that Ric Flair recieved during his 2001-2008 run with the company (a maximum of 15 dates per month). The money part wouldn't be a big thing (since Sting is pretty well off already), therefore I'd offer him a standard $850k downside (which is near enough to what he recieves in TNA), 30% merchandise royalties and the usual PPV bonuses and other perks that WWE talent recieve.
Once this was sorted out, I'd put him into a program with the "new" NWO (if that comes into fruition). Sting would come in to assist Cena and Punk during a beatdown and together they would clear the ring. This would result in a 3 on 3 tag match (Cena, Punk and Sting vs Triple H, Alberto Del Rio and Kevin Nash) with Sting getting the win.
The reality of the situation is that WWE could only get a couple of matches out of Sting and they would only be prepared to sign him to a legends deal. This way they get a couple of big pay offs from the matches the freedom to create Sting merchandise. It's all about the money.