We use Best Offer on most of our listings, but that doesn't mean we will accept it.
Nearly all of our listings are sold below the list price, and we always consider offers that are reasonable and fair. We check if the offer is acceptable based on our purchase price, age, popularity of the piece, and length of time listed. Perhaps they are basing their acceptance or not, on these ideas too, perhaps they don't have much room to move in their price? Although like you we think that this is a bit strange to set up BO and then will only accept offers so close to their price does make you wonder why bother at all.
So do understand where you are coming from, but unless you know the sellers reasoning hard to judge, maybe if it is something you really want, message the buyer and see if they will talk to you. Many sellers are happy to chat and explain their reasons, and include an reasonable offer in your message too you might have a bit more success?
We send counter-offers when the offer doesn't work for us, and this is often accepted by the buyer, so we are both happy. We do our best to try to find a point that works for both parties. If this is an item that you really want you have nothing to lose by sending a polite message and explain your position and who knows they might accept. Good Luck
