Now, I know the game is buggy at the moment. I found a way to take advantage of one of the bugs [hint hint nudge nudge, Hull]
Not sure EXACTLY how this went down, but...
I took a trading mission from Earth to the Jupiter Outpost. Upon arrival, it said 2 missions were completed, and my cargo was "-5/6"
I kept doing these delivery missions, and my cargo would always go negative. I ended up with -36/6 cargo. I took advantage of this, earning nearly 8,000 credits every time I transported goods from Lunar Colony to Arctica.
If I were you, I'd take advantage of this glitch before Hull decides to take care of it.