Well, apart from sukants reply, most of these prices that are there in the market, eg 4GB XMS3 for 1350 or G.Skill Snipers for 2650 were one day rates from prime. Was actually thinking these were market rates, even i said to others that the prices for new were less from prime. now the prices from prime have gone to 1750 for XMS3 4GB and 3200 for G.Skill Snipers 2x4GB, when i inquired last week.
So ppl who got it at existing rates and also at lower rates, will sell it for around 100~200 bucks less than market rates. simple. And we feel that they are overpriced.
Also, another point is that those who want to get rid of their stuff ASAP, will give low rates. I did the same, sold my 2x2GB XMS2 for 2500, despite having bought it for 3.85K. But buyers for such stuff are less, it might take some time to get rid of it.
Finally, I feel that after selling the item, some ppl remove the price for which they sold the item. This must be frowned upon, as if anyone wants to list a similar item, he can use the previous info as a guideline.