Great numbers don't mean that much for players like Goeddel and Asher.
Especially Asher, who had good numbers when he came back, but his value is totally dependent on raising the velocity of his newly discovered two seamer (i.e. 87-89 worked last year, but for the long haul needed to be in the 90-91 range b/c changeup and offspeed work off FB velocity).
Goeddel could hit .300 in AA ball and he'd still have little value. He'd have to be lights out as a hitter to have value, and then you still have to project from AA to the majors. Look what Pullin did last year, and he has little trade value right now.
Look how little they got for Sev, who was throwing in the 93-94 range, had a K per inning in the majors and a respectable FIP at age 23.
But unless he refines his offspeed stuff and command and goes back to being a starter, he doesn't have the typical late inning RP stuff. So he had limited trade value.
Garcia on the other hand has stopper stuff if he perfects that splitter and improves his command, touches 99, combine that with a splitter and slider that he can get over and he'd be unhittable - doesn't mean he will do it - just that he's a high upside lottery ticket because pitchers do turn it around and he has the raw stuff to dominate at the ML level.
There's a tendency to overrate the value of your own prospects.
Marginal ML prospects (Goeddel, Asher) have limited value because they're basically replacement players even if they pan out.
High upside gambles have more value b/c if you hit on the gamble you have a positive WAR player on your hands.