Just as mentioned by Nitz, the sheet contains not only test print Pokmon cards but also MTG
Like most Magic: The Gathering cards, the value of Contagious Nim 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 (Scars of Mirrodin)
Again, given that Fuecoco is one of the most familiar faces of the Paldea generation , the shiny form card for Fuecoco will be one that many will want to have in their collection or deck, simply to have it
So technically, Mega Gengar EX is poorer than Mega Charizard EX, and it only works in odd situations where you get it kicking quickly, and Chingling is there as a buddy
Without a way to immediately kill it, you just died
As the algorithm improves and as people regrade their cards, their previous cards are unlikely to receive the same grades they had before