The OP was about asking in person. As in, how much to I talk about this ahead of time with my artist without sounding like a paranoid client with 9,000 questions and making the artist want to back out?
I have an honest question about the money conversation I've had with all three of my artists, but I'll never ask it here because of this kind of response.
The bottom line is that it is your body, and you're entitled to ask any questions you'd like to ask. If the artist thinks it is too much, well, find someone else. Customer service has to be part of the equation if you're going to art on human skin, and the health concerns are legitimate if things aren't being done correctly.