The Tyranid Dominator's are the best example I have here.
When first beginning my foray into rt era tyranids, the Dominator had very little available for information. Limited Release, one mail order Flyer, no general release, worth as much as an average sized army in 5th edition due to the scarcity of models. I played a lot of 5th ed 40k, an average sized army being mech orientated was in the range of a grand, no way I was paying a grand for an old model. One came up as new never been used or assembled froma chap taht worked in the citadel foundry (or whatever the factory was called) at the time. I made an offer for 120 GBP he accepted and I was supremely happy having made a bargain steal literally based on what I had found and considering I wasn't expecting a yes. Then I picked another one up on ebay for about $50 USD and my mind started to rationalise the price difference. I saw others go up and acquired my 3rd for about $35 USD, I had a 4th but the guy selling was a d'bag and demanded payment inside the 3 day window before a case could be opened by ebay standards despite nothinga bout payment being made within those 3 days (I needed 5 till pay day), the sad thingw as he relisted it and it sat for 3 weeks before anyone bought it fi he needed the cash so desperately haha karma. the avareage price for a dominator comes to about $50 USD though I had seen them go for $25 when I didn't have the money or it was listed incorrectly.
Then about 4 months ago this complete tool (b-stores on ebay) hops up and posts up this:
http://www.ebay.com/itm/Zoat-Tyrani...18?pt=UK_Toys_Wargames_RL&hash=item2589fc9fc6
Yep, a Dominator at $333 USD, it was up originally at closer to $380 USD.
I was appalled. So i contacted the chap and explained very calmly about how it would be severely unlikely that he would not get the asking price at all, that I had acquired 3 dominators, could have had a 4th and had seen 4 others go for an average of $50 USD in the past year and that he should seriously consider changing his prices to reflect that. He stated that he had seena dominator go for $380 USD last week and that his pric4e reflects the true value. It's sat for more then 4 months and not shifted.
Oh look, a new listing appeared, from 'ye alchemist' on ebay (he has a lot of rare stuff - I believe I picked up something decently priced, but mainly it's all severely overpriced like dross), look how much this baby is for:
http://www.ebay.com/itm/Warhammer-4...58?pt=UK_Toys_Wargames_RL&hash=item43c5a9ad66
$292 USD. Obvious price undercutting to sell his before b-stores but woah.
This is the first dominator I've seen listed since b-stores stupidly priced one went up and it is so over-costed it is insane. The really sad part is that Dominators, at least in the forseeable future, will not be priced more in line for what they are worth and anyone wanting one, I'd advise to not pay more then $50-$80 USD for one. They simply aren't as rare as that heinous price tag suggests.
The community for Kingdom death: Monster on the kickstarter page (cannot wait!) have a name for ebay - evilbay - because price gouging is more and more common place, and it's sad. It's actually more of a push away prospective people interested in the vinatge stuff and oldhammer with vintage models because the prices are so heinous. Current GW stuff is heinously priced but when that stuff becomes as expensive or cheaper then collecting a vintage army, most people will just move to another system like warmachine/hordes (warmahordes), infinity or otherwise.