Just as how the dealers like to keep their clients confidentiality while trading right now, they would maintain the same while trading with the other faction.
War is happening with all of Arinar involved, yet all warriors have free will, hence only fair that they would like to satisfy thier greed for gold by anonymous trading through the dealer who may supply the opposing faction. In the end gold is gold no matter how dirty.
Besides the dealers aren't really the kindest of people, thier 10% taxation is alot for just being an anonymous middleman.
Making them somewhat of a neutral smuggler would explain how the items can be baught from any dealer, and potentially explain gold and item flow between the factions.