I haven't played since last July when they removed the $99 offer. But when I did play for 7 years, this thing always irritated me also. You go out of your way to be nice and help someone with a weapon or armor, and they pull this. I assume its to resell.
Although not everyone is this way. I always remember when I first played and someone just gave me an item out of the blue. I always remembered that, and did the same later to another person I met who actually did use it. In fact he doesn't play anymore, but I see the item on his inventory on eqplayers.com.