I have made a guide to mining thorium, pretty simmilar to this. But anyways, on my server the need for thorium high because theres barely any on the AH. When I was level 77, I really wanted a flying mount so I decided I well mine, and I did. When I checked the AH for the price, I noticed a price range between 40-70g a stack for thorium.. That's pretty much 1/2 the price of Titanium ore but you farm it x4 as fast! Your looking at 400-800g a hour.. But, there is no flying mount which is a bummer, but if you don't have a epic flyer it is better money.
This is more aimed towards people 60-70 rather than 80. Not everyone has a 80 they can farm with, I play on two seperate servers, and money is rough.. So this is pretty usefull.
Your concept is like this:
Other person: Selling a level 64 warlock for $75.00
You: You can easily sell a level 80 for $150
(quick example lol didn't know what else to use)