The G league, Mid European League guys are staying-so they are not Elite College, but I would say stars at some level ?
Where it gets interesting is guys like Henri-who " just might " get a guaranteed first round contract-and be a step closer to a"real" contract But they don't really know . In Henri's case he would make more next year staying in all likelyhood-but he "could " make more in 2-3 years going.
Since I brought up Henri it also likely has to do where their life is at. He is getting married. He perhaps does not want all the drama another year of Can he be a first rounder. If he does not get a guaranteed NBA contract perhaps he can just move "home" to Europe and play a few years until he has to get a"real" job