A video by well know American writer Harlan Elison (Star Trek ep. "City on the Edge of Forever", Bab 5, several Hugo and Nebula awards)
He very aptly gets the point across that your time as a writer, or photographer, or artist, is worth something. And if you ever have a moment where you think, "meh, I will do this one for free..." play this video. And if they don't call back because they didn't get the freebie they wanted from you... well so what. However, Harlan does say that more colourfully.
Just replace the word writer in your mind with photographer every time you hear him say it.
Mike Wood Photography