Seems like it is the single blisters and boxes that are going for the silly prices, at least when it comes to chaos and imperial. Did see an eldar fleet worth maybe £100 new go for closer to 300.
Generally speaking I refuse to pay over what it would have cost me from GW though getting that imperial fleet for much cheaper than I expected yesterday made me happier to put a most of those savings into my next bid just incase.
As it was that little bit extra netted me the boxed game, a couple of battleships, a blackstone, some random escorts and extra cruisers.
Also means I have pretty much spent 4-5 months worth of hobby budget in 2 days, but over all I got everything for close too or just under what it would have cost new from GW if they had it all in stock.