This is old, but since the thread has been revived, (and not much else going on), I thought it worth to mention the very weird logic in this post.
Someone said that since the artist charged $180/hour, and he or she as the customer only made $35/hour, no tipping would be involved...which as an Australian living in Australia is probably par for the course.
And then, that post happened (above). "Let's add on all these extra charges to make it look like the artist makes pennies". Um, no.
If an artist is charged a shop fee of 30%, that's fine. If it costs $40 to set up, that's also fine. But it doesn't cost $40 PER HOUR to set up does it? "Listening to what you want"...yes, yes, that takes a whole lot of money.
As someone who's done a plethora of different jobs, plus dabbles in the artistic field, *I get it*, but let's not start pulling charges out of the sky to justify an artist's pricing. I know I can pay $5K for art that would cost $1K somewhere else, and it's not because *he listened more*. Eh?