Infinite Money by Tora Magic

You show a pack of blank papers and riffle it through to show that they are all completely blank on both sides.

Then you take the stack between your fingers and suddenly and visually the blank papers turn into printed (imitation) 100 euro bills! You can now show the whole stack on both sides and riffle it (both from bottom to top and vice versa) and everything is now printed in 100 euro notes!