Hamels doesn't give you much surplus value, though...he's going to be paid what he's worth over the rest of his contract. So I think that will keep the price down somewhat. That's especially true if the Cubs and Red Sox are the two primary suitors (as rumored)--neither team is likely to be willing to empty their minor league system for him.
A wild card for the Cubs this offseason is how the front office values Baez at this point. I don't think he has lost much trade value yet, but I do think he has shown holes big enough that the front office could have serious concerns. It wouldn't surprise me that much if they were willing to move him with a couple of depth players this offseason for Hamels (or someone else who provides premium value).