Yes that is true, I have seen the Icy Dragon Sword go from 10k-20k in less then two hours. But have been offered upwards to 50k for mine, not that I am going to part with it. It got me through Faction's and Nightfall. Another idea is to watch the trade channel for a few days and see what items are going for if it's something that can't be purchased from a trader, then try to sell around the average of the prices.

House Samporna
"Base not your joy upon the deeds of others,
For what is given can be taken away"
-Peter Steel