The more I think about this, the more I think there's actually significant upside for the Marlins. Set aside for the moment that I don't actually believe that the Marlins are thinking this way.
In a sim league I'm in, we have a $50MM salary cap and always have enough cash to meet it. Basically, every team spends $45-50MM every year. When you trade established players with big salaries for prospects, you don't just get the prospects. You get the salary cap space, which you can turn around and use the following year, adding just as much talent as you just gave up. But you get to keep the prospects.
There are always new FA available who you can spend money on. There isn't a comparable ability to add young talent. So, for example, let's say that the Marlins turnaround and spend their savings in FA (assuming they could lure FA, which seems unlikely...)
Bonifacio: $4 (arb)
Blue Jays: $40.75
Net: Blue Jays take on $30.25MM in salary from the Marlins in 2013
How could they spend $30MM? Well, I just read an analysis of Jim Bowden's FA predictions from last year and it turns out that he was quite accurate. So let's use his figures for this offseason to look at some packages of players the Marlins could theoretically get. Since we're just talking 2013, I'm going to take 10% off of Bowden's AAV since contracts are usually back-loaded.
Josh Hamilton: $20MM
Dan Haren or Edwin Jackson: $10MM
Zack Greinke: $18MM
Fransisco Liriano: $4MM
Joakim Soria: $4MM
Ryan Ludwick: $5MM
Brandon McCarthy: $9MM
Shane Victorino: $8MM
Melky Cabrera: $7MM
Jonathan Broxton: $6MM
Now, take any one of those packages and add it to haul the Marlins got. Now who made out the best? I think we sometimes fail to account for just how valuable money is. Sure, teams could spend more if they wanted to, in theory. But we know that they functionally operate within a self-imposed cap. Getting both significant young talent AND significant "cap space" is a pretty nice haul. Unless the expensive players you're giving up are signed significantly below market rate (you can certainly argue that Reyes is), the money is basically worth just as much as the players. The prospects then are the price the other team has to pay for the guarantee of being able to spend that money on those specific players.
Considered differently, would the Blue Jays be a better team today if they had just signed Josh Hamilton and Dan Haren and kept all their young talent? Or Zack Greinke, Melky Cabrera and Ryan Madson?