Like most Pokmon cards, the value of Furfrou 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 (Perfect Order)
Obviously many other factors are added here, such as the centering of the print on the paper, front and back (yes, how well the design is positioned on the piece of cardboard), the quality of the holographic foil, and other parameters of which I have never had the courage to deepen knowledge
The name was likely changed to avoid the religious connotations associated with demons
Description Le Paquet de 65 Sleeves (ETB ME01 Gardevoir), un indispensable pour tous les collectionneurs de cartes
As a curious note, the cheapest variant of Sheoldred, the Apocalypse which is available right now is the Phyrexian text version