I made 100m credits within the first month or two after 2.0 launched. I've made another 100m since, but the demand is less now. I still make 1m every couple of days or so. Here's some tips:
- Mk-9 augment kits sell well. Get the components from RE'ing level 54 green droid parts, which only cost 2 metal and 2 compound.
- Grind the basic comms to get artifact ear and implants schems. They sell well, but the profit margin has dropped to less than 100k per item since B/W started giving out free artifact ears and implants with the weekly Czerka quest (they were making 250k profit per item prior).
- Crafted purple level 54 ears and implants sell decently. Get the Beryillius from purple 450 UWT missions instead of buying them on the GTN and you'll be able to undercut most other crafters and maintain a 50-100k profit margin per item.
- Do end-game PvE, especially hard mode TFB and S&V. Item level 72 armorings, mods, barrels, and hilts, sell well and the selling the crits makes millions. Item level 72 ears, implants, and relics typically fetch 500k - 1m crafting fees.
- Item level 69 and 72 enhancements sell slow on the GTN but have a huge profit margin.
- Dyes: there are dye schems that require champion or legendary standing with various factions to buy and learn, but they sell well (2-3/day) and have 50k-ish profit margin.
- The margins on stims is so low it's not worth the trouble to make and list them most of the time.
- Scan the GTN regularly for deals on crafting mats and stock up when they are low.
Hope that helps.