This is no more against the rules then buying something from an npc vendor and listing it for much more then what you paid. And if someone is immediately relisting something ill happily sell them all my supply at like 75% of their asking price. They get to feel like they "control" a market, i get a fast turnaround to clean up my inventories and can list something else. And if theyre wrong about the demand for the item then they end up stuck with it all.