The real problem is that over the past decade, or so, our hobby has seen an influx of highly naive and at the same time largely talentless (where building anything is concerned) individuals who are willing to spend any amount to, in their eyes, overcome their ignorance and modeling shortcomings. Not only are many eBay items being offered at excessive prices, plenty of them are ending up selling, even when the items are outright, or otherwise, misrepresented.
As an example, a while back I saw a Mantua milliary train, pulled by their little 0-4-0 switcher, offered as supposedly a unique example of an early HO model exhibited at the 1939 New York World's Fair. In fact, the set was nothing more than a commonplace Mantua millitary set from the late 1950's I recall well and nothing more. In the end and actually worth no more than $35-$45, at most, it sold for over $300. The auction had numerous bids and sold as a unique collectible. In my experience, this sort of situation is hardly unusual, nor is the excessive pricing of various older, formerly very cheap and commonplace, secondhand items...and they sell!
I guess if one is looking for gullible buyers these days, the HO trains marketplace can be THE place to make money.
NYW&B