Thank you for the contrary assessment "So Good ..." I think there is a strong case to be made that the Red Sox gave up surplus value in the Kimbrel, Thornberg, and Sale deals, not so much in the Pomeranz deal. There's no need to resort to conspiracy theories to explain the coverage of those deals however, as it is as simple as the media and the majority of the fan base have large discount rates on future production vs. present.
I also used to become overly attached to prospects, having been scarred at an impressionable age by the Bagwell and Schilling trades by a front office that was locked in the 1950s even by 1980s standards. In addition to age overcoming that low discount rate, I found the book "Superforecasting: The Art and Science of Prediction" to be extremely helpful in stemming my propensity to overvalue prospects. It teaches you to consider not just your preferred narrative or a small set of narratives around it that you might have in mind, but to really expand your consideration of the whole range of outcomes. And then it teaches you to place a lot more weight on "baseline probabilities" -- like "What is the fraction of pitchers rated in BA's top 10 who go on to have a career of ____" rather than convincing yourself, at risk of mixing book titles, "This guy is different!"
As you no doubt know, each prospect can project to a range of potential outcomes, right? And, each of those potential outcomes can be assigned a probability, right? And, the sum of the probabilities spanning the range of potential outcomes must be equal to 100 percent, right? So fill in these probabilities for Anderson Espinosa (and Michael Kopech), and remember, there are well established baseline probabilities for these outcomes, all of which greatly exceed 1%, even for the best prospects:
1. He never gets out of high-A ball
2. He never gets out of AA
3. He never really breaks out of AAAA status, like Todd Van Poppel, Frankie Rodriguez, Matt White, Jesse Foppert
4. He gets hurt while basically still in the minors and his arrival in the majors is delayed by up to 2 years, like Brandon Workman just had happen
5. He suffers a career ending injury while basically still in the minors or early in his career, like scores of other pitchers, including Juan Pena or Brien Taylor or Ryan Anderson
6. He never becomes more than a middle reliever because he can't maintain his velocity to late innings or never improves his command, like Guillermo Mota or Jose Mesa
7. He never becomes more than a back-of-the rotation starter during his cost controlled years, like Jaret Wright, Darren Dreifort, or Nathan Eovaldi
8. He doesn't get hurt, but loses the ability to throw strikes, like Rick Ankiel or Daniel Bard
9. He doesn't get hurt, but as his body fills out, his arm loses some of its whip, and his velocity drops rather than increases, lowering his ceiling and slowing his path to the majors (Hello, Matt Harrington)
10. He max's out as a good mid-rotation starter, like Dustin Hermanson, Chad Billingsley, or what Drew Pomeranz already is
11. He's good, but up to 2 of his major league cost controlled seasons are lost to injury, and he's doesn't come all the way back, just a mid-rotation starter like Aaron Sele or Edinson Volquez
12. He suffers an injury or string of injuries during his cost controlled seasons that consistently rob his overall output and ultimate effectiveness, like Paul Wilson, Steve Karsay, Carl Pavano, Chris Medlen or Daniel Hudson
13. He struggles as a starter but then becomes a relief ace, like Andrew Miller or Wade Davis
14. He becomes a consistent #2 starter and occasional all star, like John Lester
15. He becomes a consistent #1 starter, like Madison Bumgartner, Pedro Martinez or Chris Sale
Even though I haven't come close to spanning the potential outcomes, you must now recognize that numbers 1 through 9, all need to have positive numbers for Anderson Espinoza but are 0 for Drew Pomeranz. For each potential outcome I've left out of 1-9 that might describe Espinosa's path to the majors, you need at least 1% more deducted from his probability of being "The one who got away." Whatever fraction you put in #10, is a fraction where the outcome is, "No harm done." Of course, Pomeranz is susceptible to #11 and #12 over the next 3 years, but go do some research to determine whether they are more likely, even given his elbow tenderness at the end of last season, than for Espinosa at some point in the next decade. Bet they're not. Then, by the time you get to #13, #14, and #15, which are the outcomes you're really worried about losing from Espinoza, you have way, way less than your 100 percent probability left to assign to them for Anderson Espinoza, while you also now know that you cannot list any of of those improved outcomes as a 0 percent possibility for Pomeranz, who could be transitioned to the bullpen where he's been a near-ace already once before, or improve on his 2016 season as a starter and become like John Lester, or while much more unlikely, improve even further and approximate MadBum.