BIN - Buy It Now = No negotiation
You can have a lander set to show the BIN price and an option to Make Offer but it stands to reason that is someone makes an offer it's because they weren't willing to pay the BIN price and so therefore are trying to negotiate a lower price.
You can ofcourse just have Make Offer lander where you can try to negotiate as high as possible but in my experience buyer like to know a ball park figure before making an offer.