I bought two Aeron chairs, $10 each at separate times.
The first chair was being pushed down the street by a guy who looked borderline homeless. He was about to go into the Bowling Green subway station. I said "Are you selling that chair", he said "How much would you offer?". I offered $10, he said "great, I didn't really want to carry this all the way home". I had a pang of regret and thought I had possibly walked into some type of high design sting operation. I asked "Do you own this chair?", he replied "My office was renovating and they were throwing it out." Good enough for me.
The second chair came a couple of weeks later. I was walking down Broadway by the bull, about 100 yards from the first place. One of the street vendors was sitting on an Aeron. I asked if he would sell me the chair, he said sure, $20. As I was inspecting it, a woman walked by and said "That's a nice chair, it's not a real Aeron like they have at my office, but it's a nice chair". The hydraulic cylinder was broken on this one, the chair only sat at the lowest position, when you would pick it up, the cylinder extended. I offered him $10 and he accepted. It was a genuine Aeron. I ordered a new cylinder for this chair and it is like new, the cylinder was around $90.
Both of these sales happened within my first 3 months of moving downtown. I have never seen another Aeron chair for sale on that street or any other. I looked.