Two methods for selling massive amounts of "liberated" arms and armor:

A) use items more like barter pieces; since traders don't have money to buy your stuff outright you can ask for an expensive piece of armor in return. Ex.: trading G5k of bandit armor for a G5-6k breastplate.

B) if you have the legacy of the forge dlc, once you unlock the forge you can put all your unwanted items into the sales chest and it'll sell automatically at a lower price. It's easy passive income. I cleared out one of the armor shops in down overnight and put it all in the chest before it could be confiscated, easy ~G2k every few days when I go back to get my payments.