I've sold a couple of bikes on CL and I listed the price as "firm." They were good deals and the buyers paid what I asked. I've bought a couple on CL and again paid what was asked. I can't see putting someone to the trouble of meeting and then trying to chisel down the price unless it was understood ahead of time that the price was negotiable. It's been many years since I bought a bike from a shop, but if I were to do so I'd ask "what is the best price you can give me?" and take it or leave it. On the other hand, I understand that some cultures enjoy haggling (or negotiating) so my preference is only that.