To use this guide, you are going to need access to the high level flashpoint Directive 7 with a character that has stealth. So it certainly isn't for everybody, but you can do it solo, without any competition, unlike some other farming methods in the open world.
So here goes:
Enter D7, make your way (using stealth) to the first waypoint - a terminal guarded by 2 normal mobs.
Kill those, it's really easy, and activate the terminal.
That will lower the blue barrier, so go through where it used to be and turn right.
Run/ride past the miniboss (Detector), ignore him (or you might want to vanish when you jump down from his platform).
Drop the tower by firing on the missile rack, cross the newly made bridge.
When you cross it, the miniboss should evade in a few seconds.
Stealth and continue along the right wall, watch out for patrol mobs and their detection AoE (wait until it disappears).
Keep turning right until you arrive to the blocked bridge from earlier, avoid the big bot and enjoy your loot.
Port out of it back to the entrance, reset phases, repeat.
The chest contains 5500 to 7500 credits, plus a lvl 50 item, most often green worth a 1000c to a vendor, but I have seen a few blues. The run usually takes me under 3 minutes, so that's up to 160k/hour
Video I made on YT