Personally I've found a price tag of 160g per Khorium Bar to be perfect. Sells everytime withing 48 hours. If you have engineering as a profession, you should also make a few Khorium Power Cores and list them aswell. One Khorium Power Core requires 3 x Khorium Bar and one Primal Fire, which comes to about 510g on my realm, but you should always ask for more than the mats are worth. 600g price tag works perfectly for me.
Khorium nodes can be found everywhere in Outland, but to make one spawn instead of the regular Fel Iron or Adamantite deposit requires luck or time. They are more rare than titanium nodes in Northrend, but usually 6 ores can be found within 30 mins of flying on a epic flyer. Better way however is to buy up cheap ores from AH, smelt them and relist them for their proper price! It's quite safe bet, so no big risk involved in monopolizing it.
They will go, but not instantly, so have patience!
Gonna mine it instead? Here's a tip!
Download the following addons: Routes, Gathermate 2. and the data file for it.
After that, choose where you want to farm it (a good spot would be Nagrand or Netherstorm), open it up with /routes command and create a new route with the "add" option. When you're done, a new route will be shown on the minimap showing you the most efficient way to look up for every selected node. Works for chests, herbs and other interactive items too!