I started working in a hobby shop in 1970, when many of the products in question here were still on the “new” market, and some others were not considered that old.
Today it really depends on your interests and modeling style. I have lots of “vintage” HO, and there is a lot of it I would not have on my layout.
I’m selective, I don’t “collect” it or maintain its original appearance or condition. I will weather an Athearn metal kit from the 50’s just as fast as sometihng made last week.
And I do upgrades and add additional details to many of the older models I find acceptable.
Many I have owned for a long time, others I have aquired along the way, mostly at shows or a few shops I know that deal in that sort of stuff.
I have posted pictures on here of unbuilt 50’s and 60’s kits that I have. They will be built to my requirements, again with no concern for their “history”.
I find prices to be all over the map, and I am someone likely to pay as little more for the more “perfect” pieces.
You will not find me even slowing down for the soda carton full of unboxed freight cars at the train show. If it has been handled/treated like that, I don’t want it.
I’m looking for those “practically untouched” pieces, still in their original boxes. Not becuase of any “collector value”, just becuase I want stuff in good condition, not messed around with…
So, I pay more, for the best of the best of what was out there in 1950, or 1960, or 1970.
And it runs right along side my brand new RTR this or that, or the resin kits I build, or the high detail kits like Proto, Branchline and Intermountain and the present day “Athearn blue box” grade products. Because not every piece of rolling stock needs to be a museum piece, they just need to be reasonably representitive.
Prices - supply, demand, opportunity and desire to be rid, are always the con