AskMecha: Another tipping etiquette question →[More:]

So I know if you get your hair cut by the owner of the salon, you don't have to/shouldn't tip. Does the same rule apply for tattoos? Mr. is finishing up the shading and color on his half-sleeve tomorrow, and everything's looking phenomenal, but our guy is pricey ($175/hour) and it's already costing a small fortune. Are we expected to tip? If we're not, would a small tip ($50-100) be a compliment or an insult?