Amateur ethics 101 (wasRe: pdp8/f)

Nominally we are a "friendly" group of similar, yet diverse collectors and admirers of old computers. We are not businesses. There is a difference in what ethics are appropriate. The ethics of taking advantage of mistakes people make is very questionable to me. I give the money back if a person makes a mistake giving me change. I also take the free pie when the grocery scanner rings up the wrong price. Some transactions deserve conscious consideration of the ethics before acting, but the situation above I think is pretty clear. I would not accept an item with that much value without telling the person and giving them a chance to reconsider. If I really wanted the item I would either make a "fair" offer for it (cash or better a trade, like value for like value), or bid on it with the rest of unwashed and extract some quid pro quo later on.