It seems some people just can't stand competition of any sort.
They become furious when faced with it.
I don't think an economy could exist in-game where prices remain the same all the time. They fluctuate based on many different things.
Something's worth to one person isn't the same to another. It's not something to be angry about though. This is just a game. If people are selling an item for 40k, and I want to get rid of mine and make some quick cash I'll sell for 30k. If they go 25, I'll go 20. I want my things sold fast. As long as I'm making a profit I'm happy.
Also, if it's a lower level piece of equipment I don't feel it should be so expensive that new people have trouble affording it. I may decide my own price of what I think it's worth without even looking at what other people are selling for.