Ya know I think mugs and corresponding prices have to be separated into two very distinct pots. A labor intensive mug with hand carving and/or hand painted can absolutely fetch $30-$50 even at the small shows I do. Its a beautiful pot that folks that enjoy pottery and coffee can use, appreciate and admire every day.
BUT a nice dipped large mug I just don't see it in any numbers. I need to move dozens, as mugs are my main thing and any time I put a price out of the teens sells plummet, People admire and compliment and you can often see them trying to justify as they pick up and hold and admire. $20+ is just a lot for the average person to justify for a coffee mug. At $15 my tri-dipped are just fine labor wise as I have about 20-25 minutes in a mug these days.
I should clarify I do pedestrian shows with booth fees mostly under $200 and are not high end art shows. I am aslo in the south not on the east coast.
I have settled in at $15 for large mugs and they sell in much better numbers and I average 2.5 mugs production an hour which is prob $25 an hour after show and other expenses deducted. I have just made this determination starting this weekend and I think I will stay there. I have tried $24 down to $18 and mixed in discounts for multiples and the flat $15 seems to work.