Pauly's plan was never revealed. It does seem odd that he would ask for more money if he was just going to flee with it, but his motives were never made clear.

I just watched this episode and noticed the same thing!

Pauley's last words, before Devlin "pays him in Full": "You're here to buy guns. I don't have to account to you."

Such an oddly condescending thing to say, considering he was the one SELLING the guns, and planning on cheating his customer besides. But he's definitely slapping a magazine into that Mac 11 before he gets gunned down. If Devlin hadn't been a terrorist, this particular murder could almost have been considered self defense!

That's very true, he could've avoided jail at all if he had called the police immediately and claimed self-defense, but indeed that wouldn't have been good for his terrorist endeavours.