I didn't think there was much of a market for counterfeit celluloid balls especially since the main ones being used these days are 40+ Poly balls not celluloid.
doubt they're fake, people aren't looking for celluloid ball deals because the deals are everywhere for them now. only way to know for sure is test them. give them the wobble test
Have you played with them. If they play okay, they are not fake; they are real. If they are really really bad and you feel like they have no right being called 3 star balls, then they might be fake.