"AKG K340 Electrostatic Dynamic Systems" used pricing?

[point3six]

Unexpectedly stumbled across these headphones at a friends and he gave em' to me for 10 bucks. I saw that they were AKG, which automatically heightened my interest. After doing some brief reading on my iPhone, I decided to make the purchase. I couldn't find any definitive price as they seem to be essentially off the market. Any idea on what a used pair of these headphones goes for? I heard when accompanied with a very powerful amp they can be quite lethal.
 
Looks to be this headphone right here.
 
http://www.head-fi.org/t/186187/fs-stock-akg-k340-dynamic-electrostatic-headphones
 
 

 

[Kukuk]

I've seen them go for $180-$250, so it sounds like you got yourself quite a deal.