I think he'd give the Cubs a discount because of how much he loves it here. If he's reasonable, I'd re-sign him. Something like 3 years 20-25 mil or so. He'll probably command more than that though on the open market.
Thing is, I'd rather keep Marquis for now. He isn't pitching terribly at the moment. I'd prefer to hang onto him at least a few more starts. I don't think we'd get much in return anyway.
I think it's just the fact a lot of people didn't want him on the team to begin with and since he's been fairly average and not anything spectacular, people hate him.