I created a new single player world, and was checking out the trade guild shop. I noticed that they were selling faction modules for 1c and buying them for 1603c. I was able to rapidly buy and sell them in batches of 1000. Buying from the trade guild and selling back to the trade guild. Enabling me to slowly take all their money.
It seems very exploitable for a faction to buy a product for a higher price than they sell it.