[glorioushubris]

It can vary a lot.

If a short story is made into a movie, the first step is for the production company to secure the rights to the IP. This is usually done through an options contract, wherein the writer sells the production company the exclusive but time-limited write to make a film adaptation. When their option period expires, the production company has to either renew the option for more money, or give up on the project.

How much money an option sells for depends on the profiles of both the author and the producer/studio involved. My first option contract for short fiction was $2500 for a one year exclusive option--slightly more than I made when I published the story originally. My most recent option contract was $12,500 for an 18 month exclusivity period.

Authors with large backlists can have lots of option contracts always expiring and renewing, and often have this as a meaningful income stream even if nothing ever actually gets produced.