OK, it is 1960. You walk into a train store to buy some trains. The shopkeep has on their wall new trains from the 1960 catalog, some still new 1959 inventory left over and used inventory they have taken on on trade. Two items spot your eye, the 1956 6464-325 and the 1953/54 6464 green Rock Island boxcar. Both items are in top condition, not new but well taken care of.
Today, we know the 6464-325 boxcar is a hard one to find, so we would expect to see it at a much higher price than the 6464 in this example. So ignore what we know today, it's 1960.
I don't care what the price was in 1960 for these items, but was there a price difference between items like these, common and rare items then? Would the these two items have a multiple of 5 or 6 between them even back then? If not, when did the prices seperate to have such a large price difference.
Given your premise that I 'walked into a train store to buy some trains' I must assume that I am a kid and not an adult collector. Never met the collector that went into a store to buy 'some' trains. Ergo, there is little if any difference in the price I will pay.
Forward to the 70's when I am older and a TCA member at a meet. Now I am a collector and don't know any better so I am willing to pay a difference in price based on my 'need' to own the rarest of the rare.
Both times I purchased a brown double door automobile car from an individual I did not pay more than I would have paid for the blue car. The first time I did not know any better and the second time I did but still did not pay more.
Several months ago I was in an antique shop in Corpus Christi when on the floor I saw a box of trains. It was a 671 Steam Turbine Set like the one I got from Joskeys in 1952. The manager walked up while I was telling my wife about how I had carried the set home in my lap back then. She walked away, made a phone call to the booth owner and came back with a price of $100. At about two and a half times what my mother paid in 1952 I gladly took it. When we got home and I was putting my childhood memories on the table, in the bottom of the box was a AA Erie Alco from the same period.
As a kid I do not ever recall saying that this engine or car will be worth a lot more someday. If fact I don't say that today. Trains are toys, sometimes big boy toys, but nevertheless toys. People collect at their own peril. If a box car is worth five or ten times the average price someone will reproduce it. Oops, sorry, Lionel has already done that.