You arent understanding. With a second hand product, prices are always slashed big time unless its something that everybody wants and its alternatives arent available in the market. Which isnt the case here, nobody cares for a X2 3800+ being unavailale. They would just buy a 100Mhz faster processor. Your price will have to go down.
Tell me about warranty, condition, use, box and everything. And I might buy it for 3,500rs if you are in Karachi.