two theories:
1) It's a scam by the auction house. There's no such thing as a talking Chocobo, or a Robot Imp. But they're rare items so they tote them out every now and then to attract other customers.

2) The guy use to be a frequent customer at the auction house, he was good friends with the auctioneer and all the staff loved him. One of his favourite memories was the day he bought a talking chocobo for his son (at a reasonable price), the look of absolute joy on his son's face filled him with contentment. However he develops early alzhiemers and now spends his days confused. The son takes his dad to the auction house every day because it's his favourite place and every now and then he works with the auctionner to set up a little re-enactment for his dad to get him to buy the chocobo again for him so he can remember how happy he was, of course the other customers bid on it too so the son always places a ridiculously high bid (knowing he won't have to pay anyway) so he can pretend to be super excited and see the smile on his father's face. Unfortunately the talking chocobo dies in the two year gap between the world of balance and the world of ruin which is why the son tries to re-enact it with the airship model and robot imp.