If I agree to a price, get there and the machine is completely misrepresented, I speak my issues and just say I am going to pass. If they then want to reopen negotiations, then I may or may not be game. Usually I am pissed off enough that I don't even want to bother.
Had once made a deal on a Bally KISS from pictures only. It was in Ft.Wayne. The guy was very good with his camera angles that I could not see that the front of the cabinet had been kicked in at one point and he had fixed it with bondo and/or wood filler. The coin door frame wasn't even sitting correctly. I get there , see this, and just say sorry, this isn't the machine as you described. His jaw hit the floor and questioned that I was just going to walk away after driving 4 hours. He then asked "what's it worth to you? " I said $500 as I was walking away. He laughed and said not a chance. 3 weeks later he called and asked if I was still interested at $500. I said nope, I offered $500 right then and there.