question about pricing

[lizziebelle]

I've had someone contact me to ask me if I'd license one of my photos for a self-published book of his. He said he's planning to print about 250 copies. I'm flattered, but I don't want to give it to him for free. How much should I ask? I've never done this before. I don't want to ask an unreasonable amount, but I don't want to ask too little, either.

Thanks!