You do how the black tulip mania ended, don't you? The crowd madness all of sudden collapsed completely overnight without any specific reason, prices of tulip bulbs plummeting to only a fraction of what they were before. It caused a lot of people to lose lots of money or even go bankrupt. I'd call it the first documented pyramid scheme (or scam) in history, caused by speculation fuelled by greed of the 'not so initiated' in the trade.
Something similar has happened with another hobby of mine, collecting (Marklin) model trains, which I've been doing since the 1970's. About 20 years ago model trains were discovered as a good way of investment, with predictable consequenses for the 'esteemed value' of items. Right up to pure speculation with certain models built in the 50's and 60's (like the CCS800 Crocodile locomotive). The last couple of years common sense has gradually sunk in along with (or maybe because of) a flood of collections for sale, eg. after a collector's death, and the investment hype quickly faded away. Because of this prices have been falling ever since, especially so with the models that were once regarded as a good investment item.
Personally I have never really cared about the value of my model train collection, just enjoy the beauty of watching them on display in the cabinet on the wall. Never felt the urge to get carried away in the investment hype, and pay overinflated prices for specific items just for the sake of owning them, either. Value is just a matter of perception and a result of your own definition.
The 1200XL madness will probably fall through as well. Until then, if you don't think the items on eBay are worth the asking price, just ignore the gold digger sellers and let it pass.