Lv. 50 Sage here
400 Slicing
400 Underworld Trading
400 Treasure Hunting
From slicing I often get "green"/uncommon "Strongboxes", (about 50/50% if 7500-10.000 affection with companion) 1 uncommon Strongbox contains an appropriate amount of 3.500 credits. The cost of an average mission is between 1100 and 1700 credits. So that's around 2000 credits per companion per half an hour. This is 4000 per companion every hour, assuming all 5 of your companions are more or less in love with you. Conclusion: strongboxes alone won't make that many credits, however - if you pick up those world-strongboxes you can easily add 20.000-30.000 credits to your daily income.
That said, you also get "other" stuff from slicing. Slicing is good for, well, everything. I have a whole cargo-slot filled with lv. 340 (max) epic crew-skill missions. With 7500 affection or above, my companions can ensure me that they will return with atleast: 3 different epic grade 6 materials, rare/epic affection-stuff, maybe another epic mission to repeat the process, epic lv. 50 augments (these are good for Cybertech I think?)