Sometimes you make a sale that just shocks you. Then is shocks you even more that people do it over and over again. Abyss Crystals was a hot item for me before they started to crash. What I would do is post them in stacks of 6 with a 30% mark up and they would sell. Thats not a small purchase and I thought the exceptionaly high price on that would give people some pause.
This stuff does not happen every night. It could go weeks and I was not in a rush to sell them. One weekend I sold 3 stacks like that. It would be one thing if the stack of 6 was the only thing up, but that was not the case. Most of the time I see lots of single stacks still up when I go to collect my gold. It worked because I was the only one that ever posted a stack of 6.
A more recent one is parchment. It's not a big seller. I'm just more shocked that it sells at all. 4 times in the last 2 weeks I have sold a 50 silver parchment for 9G. This is like thread that you buy from a vender. I got a few screen shots of it.