how rare do you think was exodia in-universe?

[Fantastische Hure]

in the manga, if any1 can & wants to answer.

 

[SSJ2]

There was only 1.

 

[Pyro]

Probably top 5 rarest cards ever printed, at least in the original Duel Monsters and perhaps GX (don't know much about PoopDs and beyond). Weevil stated he had never seen a single piece in person and he was one of the top players in Japan (or even the world) at the start of the series. For him to have never seen even one piece physically is ridiculous considering the money he presumably was making from tournaments and such.

 

[Papasmurf]

Each individual piece is about as rare as the Red-Eyes probably. Maybe rarer in the case of the head since it's the only Effect Monster and the one to specify that it provides absolute victory when all five pieces are in the hand.