With the amount of security mechanisms in a banknote that have to be tailed to each design, I would assume that making that many variants would be financially irresponsible.
As someone with the detection mechanism tatooed on their arm, I can tell you this is not based on the visual design of the entire note, but on a small constellation of five rings, the so called EURion constellation [0]. It's also used by other bank notes around the world, inlcuding the Yen and US Dollar.
