there has to be some looney people involved in this.
Lets face it, this is a hobby. The trains are not investments, they are the cost of having fun. You might luck out and sell some for more than you paid. But most are not going to be treasures to fund your retirement.
I think especially with the electronics in this stuff going obsolete in 5 years or so, the value of the modern stuff won't go up. What can you do with it when the smoke gets out of the circuit board and you can't get a replacement? When PW trains were much in vogue, you could repair or have someone repair about anything and restore it. And most stuff still ran on the same control systems. Now there are so many controls systems, and so many no longer supported, it is hard to figure out what makes it go!
Seriously, model trains, like automobiles are a cost, not an investment. if you look at it that way, and you won't be disappointed and if someday you sell some and think you did well, you will be very pleased.
