Thanks for the responses. I ended up giving them $100, which I think is more than 20%of the value, but it was well-earned because the kids loved it.

50-60 bucks. They use gas to get to your house, etc and it’s nice to let them know you appreciate their time

20% of the value, not what you paid.

We “bought” a performance for a kids birthday party at a school auction. IOW, we paid about half of what what they’d ordinarily charge. How much should we tip them? If we’d hired them normally, we’d tip 20%, but should we tip more, since they’re not making any money from working this particular party?