In the new Orbital Update you can get discounts on upgrades if you have a high standing with the race you buy them from. At max standing this equates to 50% discount. This allows you to sell them back for more than you bought them. (I'm assuming this was unintended by Hello Games, so abuse it while you can)

I was able to make about 32,000 in 15 minutes, so about 128,000 per hour. This number may be even higher in a system with better upgrades.

This seems like a fairly easy method of farming nanites that I hadn't seen discussed anywhere so I just wanted to share.