If, despite good advice, the OP wants to sell his gfx card, that's up to him of course. But the fact is that people buy second-hand because they are looking for a bargain, and 6.5k is too close to the normal retail price of a new one. He's probably the seller who's offering it on eBay for a starting bid of 6.5k auction and 7k Buy It Now, plus 250/- shipping.
A few days ago, I bought a 5-month old normal (non-eco) GTS 250 on eBay for 4.5k including shipping. Unfortunately, the seller dropped and damaged the card while packing it. We cancelled the deal and he immediately refunded my money.