I make about 10-15k day with one (my only) account, as long as i bot all the time I'm sleeping or working, and use different methods to not flooding the AH too much. I usually change farming place every day:
Day 1 - Farm uldum no-cinderbloom route (elementium + whiptail + some cinderbloom still)
Day 2 - Farm Vashj'ir mining+herb profile (obsidium, stormvine, azshara's veil)
Day 3 - Farm Hyjal obsidium route (cinderbloom + obsidium + little stormvine)
Day 4 - usually AH is flooded with my auctions, i usually do something else (like fishing, leveling an alt...)
Change auction posters every day you post stuff, set a limit to 20 stacks of each product, do different things with ore (ex: obsidium you can post 20 stacks of ore, 20 stacks of bars, prospect and cut 20 stacks of ore, and vendor other 20 stacks. Elementium can be smelt into bars, into hardened elementium bar, propected, and sold as ore).