I generally won’t offer below 2/3rds original asking price. Pretty much for anything. Most people if they are serious will respond to that. If someone is 2X fair market then I don’t even bother offering as they are not looking at the same value guides I am.

What really irks me though is the postings saying “make me an offer”. This usually means either 1) auction or 2) guess what number I am thinking of. I have never once had a deal work out from that starting point. To all sellers either state what you think it’s worth to not waste everyone’s time or actually go list it on eBay auction site if you really don’t know.