As is tradition, all results are ordered by EDHREC score
Since Prize Pack Series cards are only available to Pokemon TCG competitors, these cards are more exclusive and not as widely available, even on the secondary market
This could be highlighting certain Planes (such as a cube that uses cards from all sets that take place in Ravinca and/or cards that depict the plane), characters within the game, being a tribute to a specific Standard environment, or be limited to cards with specific printings, such as retro frames and white borders
Treat it as a solid hold tied to Gengar's long-term popularity, not a quick flip
There are only so many five-drops you can play, though, so its not an easy puzzle