While in the Eros Station I was able to duplicate inventory items - thus you could easily gain credits without work.
1) At the option menu (Choose Shop, Bar, Ship Modifications, etc)
2) Select Shop (this is the key) Change the status of the shop to "Sell"
3) Close the Shop Windows
4) Press I to open inventory
5) Left-click on any item in your inventory and it will disappear
6) Close inventory
7) Click on Shop button
8) Left-click on items in Shop and they will restore to the players inventory
9) Close the Shop window
10) Press I to open inventory
Whatever was selected is now duplicated in inventory. I was able to duplicate the relic item, minerals/gems, unopened cargo boxes. I did not try everything, but expect the inventory subroutine needs to be checked.
Update: It gets even worse with stacked items like crystals. If you send a stack of items (e.g. 5 rubies) to be sold it will appear in the Selling screen as 5 rubies, but returning them to the inventory (essentially cancelling the trade) returns not 1, but 5 rubies to your inventory while decrementing the Shop inventory by 1. Thus you can exponentially increase your inventory. 5+4+3+2+1 = 15 are returned and you now have 20 (original 5 + 15).
When returning items from the Shop the value returned can deflate the cost of goods to the point of becoming a negative value (thus quickly depleting the players credits) if the transaction is conducted.