Forrest J. Ackerman wrote not just the
shortest science fiction story ever, but what may be the shortest
SF story
possible (if you ignore the
title). The title is "
Cosmic Report Card: Earth." The story is:
F
For this he was paid $100 for the initial sale, as well as for four more sales, so he was paid (he estimates) at a nominal $500 per word per sale, or $2500 per word for all five. Not bad for a night's work, especially in 1973.
Source: Mimosa 16, pp. 4-6