Given that these don't really get released with much fanfare or publicity outside of here and Dark Shadows fan circles, my guess is that these are folks that don't realize that it's going to be re-released.
Coupled with the fact that the publicity for the new movie sparks nostalgia for the original property, and no merchandizing available other than this figure, the 12" one and the model kit. I'm sure more casual fans only want Barnabas anyways, and it's the more hardcore collectors that want the other characters, which appears to have more than enough to meet current demand since Angelique and the werewolf are selling for retail and under.
This is really funny, someone is selling one signed by Johnny Depp.
Dark Shadows Barnabas Collins Action Figure AUTOGRAPHED by JOHNNY DEPP!! RARE!! | eBay
Dark Shadows Series 1 Action Figure - Angelique Bouchard 815564010019 | eBay
Dark Shadows Werewolf Action Figure - SDCC Exclusive | eBay