I was asked to do pre-show backstage photography for our local performance of Rocky Horror Picture Show this past October, because I'm friends with several of the cast members. When I asked if they could get show tickets for me and my wife, the show organizer said "Sorry, we're all out of complimentary tickets" to which I replied, "Oh, then I guess I'm all out of complimentary photography services too."
I paid for my tickets out of pocket, sat in the audience, and took photos of my friends on stage. And I made sure not to take any while that event organizer was on the stage.
Anyway, back to the original request, if you're looking to get into this sort of thing for money, software like FotoQuote can give you realistic pricing estimates based on actual industry practices.