As LDS missionaries, we ate "gyoza" by the dozen especially from the Osho Restaurant Chain (餃子の王将) in the Kansai Region of Japan. The popular "Osho Challenge" was to eat 60 "piping hot-off-the-grill" gyoza in 30 minutes. Challenge champions were celebrated with a free meal and a polaroid on the wall.
I did it in 18 minutes (my companion didn't make it and had to pay up--$7.50 in those days... $22 today!) but the franchise record was set by a sumo wrestler in downtown Osaka. He ate using chopsticks in both hands and finished in 3 minutes!
At the "Shortie" snack bar back at Camp Casey, a plate of yakimandu will set you back 2,500 won or $2. Sadly, there is no mandu "challenge." But one in Australia for $50!
Happy Thoughts: The 56th and 57th gyoza were the hardest... I almost lost it! My motivation? I didn't bring any $$!