As for the price, its probably hype coupled with nostalgia and maybe some FOMO
(1) If this card is Special Summoned: You can draw 1 card, then you can destroy the 1 face-up monster your opponent controls with the highest ATK (your choice, if tied)
Mostly, we're looking for admitted mistakes in the art, weird choices made by the artists, or instances where the art doesn't totally represent the card
Surprise Stax is like surprise taxes
The price point on the less interesting cards will fall towards a buck or two, but probably not drop much below that
Kaalia of the Vast can cheat it from your hand (since it's a dragon), Yuna, Hope of Spira can bring it back from your graveyard (since it's an enchantment), and Esper Terra can copy it and trigger most of Bahamut's value by advancing three chapters: Summon: Bahamut isnt legendary, so Esper Terra has no problem copying it