It is not a matter of 1 bidder or 5000 bidders...it is a matter of 1 overzealous unsophisticated (re: inexpirenced) bidder who has no idea what the fair market value is vs. 1 bidder who is saavy as to what these things are worth and what effort there is.
In a private sale there is much more personal interaction plus the item is physically there for inspection. This alone makes a world of difference and the unsophisticated buyer would be a little more cautious to purchase reguardless of cost, where as on ebay an unsophisticated buyer can get "caught up in the moment" and way overpay for what would be otherwise junk.
Also the buying model is different between ebay and a private sale. In a private sale the buyer sets his price for aquiring the item based on a myriad of personal factors and attempts to aquire it as cheaply as the seller is willing to let go. Onsite competition is very rare and other things can be worked into the price on the spot (such as taking it that day vs holding it a set period of time). The advantage in this situation often lies with the buyer not the seller. On ebay you are competeting with other people looking to acquire the item and have completely different circumstances than you, which means the seller ALWAYS has the advantage unless what he is selling is unsellable. In a private sale it is very likely you could have convinced the previous owner to take $50, but on ebay $178 is a low price.
Ebay is bad for market value because unsophisticated buyers can cause spikes in price by overpaying that leads other sellers into beliving that if one is worth this then they all must be worth this. Just because one idiot is willing to pay $10000 for a kawiyamazuki doesn't mean everyone is actually worth close to that.
as I don't believe it makes any difference to the items perceived value, whether there is one bidder or 500 bidders...the true value is what someone is prepared to pay for it----period....
This is like saying you do believe in santa claus (and BTW I love christmas). To think that the selling venue doesn't make a difference is naieve.
One of the main flaws in your valuation principle is that you have not defiend "true value". By what you are saying true value only exists to the buyer, because other factors can make the bike worth more to one person than to another. Sometimes it is location, sometimes it is sentimentality, sometimes it is just a missing widget. If you were asking other people for the true value, then you are asking for people to guess about personal things about your life (BTW way to put in your location would would have been one of the factors). You can't ask anybody else what "true" value is because it is personal to you.
What you were asking for was market value...(which location does play a factor in also so once again way to list were the bike and you were). But market the auction market is much much different than the private seller's market for reasons we discussed before. Market Value for a junk cb350F in america is very low, in OZ it may be different because of the rarety of the bike. Also are you looking for its market value as a parts bike or as a resto canidate?
so there is a lot more to think about then it is just what someone wants to pay for it....but that is part of it....
My personal feelings on the cb350f, as a former owner, is honda could not have made a bigger dog of a bike and the public largely agreed by it not selling well and being a 2 year model only. In OZ they must have felt the same way since they are even rarer there (although from my understanding vintage bikes in OZ are just rare in general). Good and rare are not mutually exclusive and in the cb350F it could not be more true. They have what I call "Edsel value" where they are worth somethng because they are different and sedom seen, but not based on how "good" a bike the are. The only thing a cb350F is good for is sticking a 400F motor in and building a semi-sleeper. If every 350F suddenly spontaneously combusted tomorrow I would find that quite amusing.
