I can't see any reason besides misinformation and how easy it is to get money for some of the prices we have been seeing. My main concern is how new players can reproduce these misinformations and create a bad environment not only for traders, but for other new players who may be injured by more experienced trainers taking advantage of them. As JollyolNathan said, the market will adjust itself naturally, but damage, which could be avoided, may be done in this process.
This server seems to assume that everyone in here is already experienced with pokemon, which is not the case. My suggestion would be to link the new players, as soon as they log in, to a guide explaining the basics of battling, what influences stats and how to judge if a pokemon is good for the role the player intends to fill in his/her team.