Both Kazmir and Ryan deals are equals in value received (bupkis) but Ryan had so much longer a career as a dominating pitcher (even if considered an innings-eater, which he was, too) that I think he maybe answers the OP here, in terms of "numbers of World's Championships his loss cost the Mets." I think Ryan's peak was higher than Kazmir's too, and he repeated that season about a dozen times. Why, in this exercise, would we attribute Ryan's entire career to the Mets after undoing the trade? He hit free agency multiple times in his career and could have been reacquired by the Mets any number of times. Accordingly, it's fair to say that 1973 Ryan on the Mets could probably yield another championship. But even if you transplant his other 1970s pre-free agent seasons back to the Mets…do you even get playoff teams those other years? Maybe 1980s Ryan puts the Mets on top an additional year but the trade didn't prevent that.