I'm content to have a bit of confusion reign if eBay eventually sorts things out to make final "Best Offer" prices invisible generally (as they say they will be doing).
I don't think knowing a particular final "Best Offer" price would prove to be of any real advantage to buyers or sellers who are looking for an indication of appropriate purchase price or market value.
Since accepting, rejecting or countering a Best Offer is entirely discretionary, any individual negotiation is apt to be fairly unique and not necessarily representative of other transactions.
In BIN and auction transactions, the final price is almost always at, or above the initial start price. On the other hand, Best Offer is, by definition, always below the asking price.
Keeping the results of Best Offer transactions confidential doesn't disadvantage buyers and protects sellers' margins, as one "Pink" pointed out. If Best Offer results were always openly displayed, eventually the downward pressure on prices would be such that no seller would want to offer it anymore - why would they?
To me, adding "Best Offer" to a listing is simply a signal to buyers that I might be willing to negotiate. Sometimes circumstances dictate that I will accept a very low offer (for example during a period of slow sales, or if an item has been listed for some time, or if the buyer is a repeat customer, or many other reasons). Sometimes I get no acceptable offers. Sometimes on an item that garners a lot of attention I'm unwilling to accept an offer that is more than 20% lower than the BIN price. This doesn't mean that the circumstances that pertain in one instance will be the same the next time I list a similar item.
I can only say that "Best Offer" has been very workable for me. Sometimes buyers simply want the item immediately and will pay the BIN price -- I try to set that price as fairly and competitively as possible. Some buyers like to "haggle" a little, and that's fine too.
I can say with some certainty what the BIN market price of one of my items is; the offer doesn't change that. What changes is my willingness in a particular transaction to accept, reject or counter a buyer's offer, which may be no reflection on the general value of the item, but on my particular situation that day. And I agree with the Pinks that that part of the transaction should really only be between seller and buyer.
