Some interesting news came out today – namely, the fact that Stanton would only accept a trade to the Dodgers, Cubs, Astros, and Yankees. With that in mind, the Cubs would be pretty foolish not to consider kicking the tires on a trade for Stanton. That said, the "value" in his contract is pretty non-existent. Let's take a look.
Stanton just finished is age-27 season (at an MVP caliber). He's owed 10/$295 MM over the rest of the contract (barring a team option for the 11th year that would add $15 MM). If Stanton were a free agent RIGHT NOW, I'm not sure he'd get 10/$295,000,000, especially if you consider the fact that he's not likely to ever have a year as good as 2017 again. In fact, the median bWAR for his past 5 years is 3.7. If we slot Stanton for 6 WAR in 2018 (which is a monster projection), and debit .5 WAR every year afterwards (a lenient aging curve), a 10 year deal at a current rate of $8 million per win adjusted 4% annually for inflation is around $347 MM. That's $50 MM in surplus value, but only if Stanton doesn't get injured (not likely over a decade), declines gracefully (about as likely as not), and assumes that the burden of a $300 million contract doesn't affect other operations (which is probably true considering the market). I think that the Stanton contract is probably fair market at this point, which means that the Cubs would have to actively want him to give much in terms of value.
Once we've established that fact, any money the Marlins send to the Cubs to complete the deal would be essentially buying prospects from the Cubs. Does that sound like something the Cubs should do? I'm not sure, but I lean against it. If we sold Happ for, say, $60 MM, I could get behind that just from the perspective of having Stanton in RF and Heyward in CF, but I'm not champing at the bit for the opportunity to part with Happ if we aren't getting pitching or something.
At the end of the day, Stanton is a luxury the Cubs could probably afford, but the Cubs need some other pieces before they need Stanton. There's no doubt they could make it work, and there will be a point when it makes sense to float some offers out there (Stanton for Heyward and Russell?), but I'm not holding my breath.