"I’d like you to write 10 minutes of music for my short film. I don’t see why this would take you more than 2 hours to write and record since it’s only 10 minutes. Minimum wage is ~$7.50, so I’ll pay you $15 total for the project. You’ll also get credit for the project which will be shown at festivals. How does this sound?"
When you charge too little for a project in an effort to get more work in the future, only to realize that you are now expected to work for that rate for the remainder of your professional relationship