Having been a collector/runner of o gauge for the past few years I'm aware the toy train market is not an investor market. Normally the majority of used o scale locos and rolling stock generally go anywhere from 65-90% off original MSRP, I've also noticed however that certain roadnames seem to buck that norm by not only holding onto their original MSRP value but frequently selling for a premium above that. I've noticed this for all manufactureers of particular roads be it Lionel, MTH, Williams, RTR, Atlas, Weaver, etc.
I'm curious why this occurs. How much of this "value holding power" has to do with those road's relative popularity coupled with scarceness of product? But if a particular road does have a track record of a certain level of sustained popularity, albeit considerably lower than most other roads, then why aren't manufacturers aware of this and increase the number of units produced for that particular road accordingly?
Cases is point generally relate to short and tourist lines.
What are your thoughts? Have you personally encountered or noticed this phenomena and why do you think it happens?