amazonia in austin texas has a mbu thats probably 20" [one foot fish, 8" of tail] they sold him once when he was smaller, and the customer brought him back when they couldnt take care of it any longer.
they set up a recliner in front of the tank so it looks sorta like a big screen tv thats always on the mbu channel. he seems to generate a lot of business that way as once people see him, they sometimes end up signing their name on a waiting list for one.
selling a big puffer would be like selling your dog, the price may not be as important as finding a good home for it.