Quality appears to not be a driving force in these decisions, which is unfortunate. Not that CD and PSP can't do nice work, but Centipede and Suntup do quality work every time.
King's relationship with Chizmar explains CD, but not the others.
It's tough to know what King could be thinking; he has complained about the exclusive nature of collectible editions (including his notorious flip-flop on CP's Salem's Lot), but continues to approve them, in quantity, year after year. If a $900 Centipede production was such a mistake, why approve the $4k PSP Carrie? Because it was easier to carry?
As for Suntup, I wonder if Suntup (not King) is preventing this from happening, as I believe Paul has said he only wants to do King books that haven't yet had special editions, and there aren't many of those.