Some sellers want to play games too, just like some buyers do. Negotiating is like ping-pong ball. If the seller can’t counter a lowish offer, then it’s not negotiating and the seller should just cut through the games and just state their price. I agree that 10-15% is what’s common. 40% off is probably way too much but the “negotiable” seller should counter to see if they can arrive on an agreeable number. “Thank you, but no. I’ll take $16K. Firm.”
I agree that low ball offers probably happens a lot less than people fear it. I think the problem with horse people trying to negotiate prices is that they let their emotions get involved too much. It’s a business transaction. If the negotiable seller walks away due to a low ball offer, that seller was not really up for negotiating a sale in the first place.
Both buyers and sellers seem to forget that if one party walks away, but they still have interest in buying or selling to the other person, there is no harm in calling them back to see if the other party will reconsider.