Ultimately it will be what the market will bear.
Oddly enough, it is just that simple.
Some of the brass items are rather decent and will be in some demand - some of the cabooses and some structures.
There were a handful of special run CVRR cars that I look for and buy when not prices above silly.
And, I do buy the older RSS3, FA/FB, and GP38 engines to cannibalize the drives to build what I want to build. Those used to be cheap,