First there are people that like "trolling" putting item overpriced too much:
revan mask at 1.000.000.000 to show hay dude I have the mask, you suks.
so the way is /ignore
Second there are people that like the risk and make some good money, last time I buy some item at 150k and selled it for 500 each one month later.
Third there are people that lower the price with no sense. I have bought the scout from CM for 50k selled back for 5milion
Fourth there are people the put item in GTN with super low price... vial of isotope at 79k and people sell some of them for 74k... this is with no sense, sell it for 78.9k no? People still buy them.
Personally i have disgust for the fourth type of person... they are really stupid.
well the majority of your group are those that may not understand the rarity or credit value of their item, or do not care and are trying for a quick turn around (quick small profit compared to a maximizing profit but longer wait).
this is the power of the free market. Someone lists a rare/expensive item cheap, people who speculate buy those items, and then relist at higher prices. people get their quick profit, speculators get theirs later on. win win.