It was super crazy for a while. I remember seeing one XM-18 listed for $1300 with CF scales, anodized hardware and a custom clip or something, I think. I thought "nobody will pay that much" and the next time I refreshed the exchange it was sold.
I wish I was immune to the insanity, but of course I'm not. I bought three wildly overpriced Shirogorovs, and while they were nice enough they were just high end production knives priced more like customs. There wasn't anything magic to them, I had other Chinese (e.g. WE, Reate, etc.) or Russian/Chinese (i.e. CKF) knives that were very similar in terms of construction, action, fit and finish, but at a fraction of the price. I've moved the Shiros on since, so if the bubble bursts I will still get to enjoy watching it pop. I suppose that's the way to do the wildly over-inflated market knives. If you really want one, get in and enjoy it for a while, then move it on before the fall.
Then again, in the grand scheme of things a knife is a pretty good thing to end up upside down on. If you pay $1000 for a knife that you could later only sell for $400, it's small potatoes. It's not anything like the pain of buying a million dollar property in 2007 only to have it be worth six hundred grand in 2009, ouch. There were an awful lot of folks in some version of that disaster . . .