I was pretty active on Head-Fi at the time and snatched up this deal when someone posted it. I think the HD800 was still $1500 at the time.
Though that is probably not even my greatest "steal", which could be loosely seen at actually stealing. I bought the Fostex TH-900 from a relatively new online vendor, and they accidentally sent me 2 of them. I checked and legally in the US when a merchant sends you something you didn't order, you aren't required to send it back. I held onto it for a bit and that company never contacted me about it and I sold it new in box for $900. I guess they were too disorganized to notice.
I'm not all entirely lucky or wise with money. I bought the Hifiman Edition X on release for $1400 and similar tier headphones like Edition XS are less than $500 now. But I still like them enough for it to be a permanent part of my collection.
IE900 for 950 AUD. Dunu Vulkan for 335 AUD Beyer Xelento 900 AUD. HD660S2 for 550AUD.
Plus an Astron SSJ007 for 1800Aud.
For anybody unfamiliar, Australian dollars are worth less than the plastic they're printed on, so these are indeed good deals