It's truly out of hand. I know of many players who have complained about it. It is a group of horde and alliance toons who are friends outside of the game. They monopolize the market, harass competition in and out of game, and make it really unfun for others.
However, this does not, in my opinion, require GM actions. It requires the playerbase forming a counter group to PvP targeted players who are part of the mafia 24 hours a day.
1) Collect their names on a list.
2) Publish the list on the organizers page.
3) Set up shifts to organize PvP groups sufficient to kill, corpse camp, and graveyard camp their toons.
Take over their territory.