He's been a 5 to 6 inning pitcher his entire career. His mentality certainly wants to go longer, but his command and efficiency don't allow for it on average.
But he knows he'll make more money on the open market. I honestly don't think it matters what team he currently plays for, he wants to hit the open market. You may be correct that it'll take significantly more to bring him back, but at this point it's all just conjecture.