That's something that gets overlooked. Trading big prospects for Yelich is, in all likelihood, a reversible move. If two years down the road things aren't working out the way you hoped, pretty easy to put Yelich back on the block and probably recoup all the value you gave up. Yeah he won't have as much control at that time but if he continues his career trajectory and puts up a couple 5 WAR seasons, he'd only be 28 and even more proven and his contract would look even lighter than it does now. He'd be worth a haul like he is now. To add to this, given your hypothetical scenario about trajectory, hes probably worth more now but the marlins arent going to get full value in a trade. Whoever gets him is going to get him at a discount as say Brinson, Burnes and a top 30 org prospect when hes really worth Brinson, Burnes, Hiura, Diaz, Gatewood in prospect value.