Fair price for a set up?

[Valentin Zukovsky]

Does anyone know what a fair price would be for me to set up my friends bass for him. He brought it to school one day and I noticed how badly warped his neck was, and he wants me to fix it for him since I've done it on my own basses. I'm thinking around $20 or so, with him buying his own strings. Does this sound reasonable?

[Brent]

I guess, I would do it for free, personally. No more than 20.