Generally speaking, the seller sets the price. They may accept a lower offer, but they may not. Each one of my firearms is for sale. Starting price 5 trillion US, payable in gold, shipping is paid by the buyer.
That happened at the one where that picture came from too. It was at a firehouse, the PD was just managing it and openly mocking the whole event as being a pointless waste of money so they didn't care at all that people were making deals out on the sidewalk.
"We The People. We the people tell the government what to do. It doesn't tell us. We the people are the driver, the government is the car, and we decide where it should go and by what route and how fast. Almost all the world's constitutions are documents in which governments tell their people what their privileges are. Our Constitution is a document in which We The People tell the government what it is allowed to do. We The People are free".