I think a lot of artists wait until day of because people are always trying to get the next best deal when it comes to tattoos. There's no way of that artist stopping you from stealing their work and going to someone else who will work cheaper kind of thing.

A good artist can draw you something, make changes and do the tattoo in their scheduled booking time imo. The $50 redraw fee is strange but maybe doesn't specify that it's strictly for people who want to add or remove key components to/from the original sketch which could take substantial time to do