First edition cards from the earliest Pokemon sets are valuable because so few people kept them pristine - and nobody hoarded them
Its all about that rumour/wish that people had back in the day that the Mossdeep Space Center would bring you to space
Brainstealer Dragon is another great new creature that also lines up with the narrative of Mind Flayarrrs, representing the stealing of enemy brains with an effect that steals cards from their libraries
This figure applies to outer sleeves, not inner sleeves
Of course, the potential of Silvergill Adept is somewhat limited by the fact that you need to play it in a Merfolk deck to cast it for two mana, and Naban isn't a Merfolk, but as the only straightforward "draw a card" Wizard in Standard, it still might be worth the effort if we can find a build to support the mixed tribal synergies
I think when people thing about the market in a bubble they jump to Moonbreon, Battle Lilly, Alolan Friends, etc and the other waifu cards but to me those are hype cards and useless to the discussion of the overall market