It isn't a simple auction. Not all passengers are equal. There are issues that make an airline not want to bump some passengers. For instance, on some international flights there are rules against unaccompanied baggage. So the passenger without checked luggage will be bumped in order to save time. Passengers travelling in groups are also preferable as they will more likely share a hotel room. That's why families get bumped so easily. And then there are connections. The passenger who will miss subsequent connections is an expensive person to bump. This seems to have been the case in the United fiasco. The man was travelling in a group (his wife was with him) and didn't have any checked luggage, else we would have heard about it being offloaded or returned to him in hospital, and had no connections to make. Such complications go beyond the simple cash payout, making a strait auction difficult.

Want never to be bumped? Travel alone but with a pet in the hold. They won't touch you. Or travel with someone in a wheelchair. They are also an expensive awkward person to bump. As I said to one gate person: "We cannot be bumped. My grandmother only has pills for the next 12 hours." That lit a fire under them. Grandma knew to play ball and suddenly looked very much older than she was.