After everything had been sold, the buyers were able to go and collect their purchases. The most common items could be picked up at pre-designated locations, so those who had bought earlier could just go and leave.
However, those who had stayed until the end could go directly to Serena to pick up their items, which was not a big deal, but it allowed them to speak face-to-face with the owner of the black market, which was a minimal opportunity to connect with someone powerful.
Several of us were guided by servants to a location where our things were. Of course, the golden cage was one of the things that stood out the most because of its size, and it's a bit disappointing that this is all I obtained.
I guess in the end, you can't expect much from mere humans. I wonder what the demons' "black market" is like. I know they have one, but I question what they consider illegal.