Tell Grandpa it's the same grade of "computer magic" that got us to the moon and put a library in his pocket. It's not all "imaginary coins" but new technologies, that can't be de-valued like his dollars.

Ask him how much that hair-cut cost him 60 years ago. Then tell him 5 cents of bitcoin today will do that 20 years from now or less. (or 5 cents of Neo, 5 years from now)