I've done it before...after doing horses, it's a pretty easy job lol. I use a hoof knife, faster for me, but that's what I was used to before I ever got goats. It would depend on how wild the goats were, how bad their feet were and, for larger volumes, how fast they can bring you the next goat. I would say $5-15 depending on where those fall. If someone had their herd on a schedule and done every 4-6 weeks (whatever that herd's need was) on the dot, and could move their goats through in a timely fashion for you, I could see $5. But not if you have to go catch them yourself. I was paid $100 for 5 goats, but it was a bit out of the way and I did help catch.
What makes goats good for trimming is how you handle them when you trim. You can make them better every time or worse every time. Also, you can train them like a horse to start with and avoid all that. Of course, their personalities matter too. Some goats don't get excited about much, some think everything is about to kill them. One of my bucks, I trimmed him once while he was laying in the sun. Usually I put them on the stand, or my bucks, I often trim wherever they are standing. They fuss a bit but I can usually get it done pretty quick.