By comparison, how much do you earn per day? I think $500 per day would be a decent income for them, but as someone else pointed out, the venue probably takes up a big chunk, taxes another, the people involved that you don't see, etc so they wouldn't be getting that amount.

And it's not like they have a 3 hour workday either, before that performance is going to be hours and hours of practice, years of training, and on the day itself X amount of traveling (more if they're international / on tour), getting dressed up, setting up, settling in, etc.