I routinely sell the missions I randomly crit while slicing or stuff I pick up for 50% less than what I see them on the market. I am mostly looking to clean out my inventory.
A lot of people are like me. We don't need the credits and are just looking to do some daily cargo cleaning. Your GTN stock market game where you try to buy low and sell high is my GTN salvation army game where I sell low to noobs.
But I admit, while I know some dude will be happy to get a good deal on the items I sell I also enjoy the thought that I make some randoms rage about profit margins.