Costs for music editing

I had a friend edit some music for me for a performance. We needed to bring the total time down to 4 minutes. He made me 2 versions, one has the entire song sped up slightly, the other was not sped up but shortened using cuts. Has any one paid for this type of service before, I'm not sure how much to offer him. When we originally discussed it he suggested $10-15, but I really think he is asking too little. I'm really happy with his work and was wondering what some industry standard prices might be. :)