This particular one is a 'what if' scenario where Arthur from 1963's Sword in the Stone becomes a spellcaster in his own right
Like most Pokmon cards, the value of Jolteon depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Delta Species)
He is up at the cash register, checking out
The legendary birds feel more similar to the egyptian gods, being mythical creatures above other Pokemon (especially considering Kanto alone), sharing the same palette, and being a actual trio
Its much the same process with sites like Star City Games, TCGplayer, Card Kingdom, etc., and a lot of the differences come down to the exact seller fees, the buylists each individual site has, and how you need to ship your cards