I had the same problem with I sold an arcade machine some time ago. Some people feel that making a low ball offer somehow secures their place in line and reserves the machine for them, then they can haggle after that. That's not the case. It's real simple, when I'm selling a machine I go through messages in the order I received them and accept the first one that meets what I'm looking to get. That always pisses off people that got in earlier but made lower offers, but that's how it goes.