I tend to disagree with the OP. There may be some odd ball outliers and certainly some rare pieces still demanding high prices, but run-of-the mill postwar is getting harder and harder to sell. I buy a fair number of collections and I'm really only paying as low as possible for them.
ZW's were selling for up to $325 each at one time. Now you are lucky to get $100. I'll only calculate the value in a collection at $50 at best since they invariably need a new power cord, new rollers, and possibly new circuit breakers and rectifiers, plus the time to fix them.
2020 turbines were getting upwards of $150-$200 each. Now you are lucky to get $100, if you can even sell one. A moving price might be more like $75 unless in pristine condition with boxes. They have shown up with great regularity in recent collections I've purchased.
The last train show that I was at a couple of months ago there were tables FULL of common black steam engines of various numbers and none were moving.
I had someone contact me with a small collection with only a 665 w/2046W tender and a couple of cars including a Great Northern 6464 (don't know which one). He doesn't have and won't put together a list of the rest of the items and doesn't really have a price in mind except a "fair price". I'm hesitant to even go look at them since it is an hour away and with tolls. My real concern is that he will be insulted with what I would be willing to pay for them. There are no boxes and condition is completely unknown. A 665 w/2046W is a nice engine and generally runs well but I already have one in excellent condition in the boxes so this would be for resale. How long might it take to sell it and for how much? $75 to $100? Here's the thing. He wants me to come and look at them as I'm the only person to have contacted him about them. 10 to 15 or 20 years ago, I would have jumped all over the opportunity to purchase this small collection.
Just my humble opinion of the state of postwar Lionel. You are free to disagree. However, I still love running them and am just going to the basement layout to find out why my 364 log loader isn't working!