The entire Einstein quote was "Compound interest is the 8th wonder of the world.
he who understands it, earns it; he who doesn't pays it."
I only read the first sentence when I was in college and thought nothing of it.
Many years passed, I was lucky to read the 2nd sentence (online, I think) and
realized I was paying instead of earning interests.
It was ironic and used to illustrate the point "A little knowledge is a
dangerous thing."