Do I Need to Tip?

I have my 3rd make-up trial scheduled. This person works for herself and charges $100 for a trial!!! I've tipped at my other trials but I really think $100 is excessive for a trial. Considering the fact that the entire amount for the trial will go directly in her pocket, do I still have to tip? My other trials were far more reasonably priced (30-60).

Normally, I tip when a service is provided, but I'm having a bit of difficulty swallowing the idea of tipping for a trial that costs so much.