So lets say you are on a server with a relativly high population. Lots of times people are never going to want to go out and farm gems for JC because its a hastle theyll just buy the lower level ones off the AH. I did some research and ran through SFK, the full clear took 9 minutes (level 80 DK)
In 9 minutes I got
Shadowgem x14
Moss Agate x6
Wool Cloth x144
On my server Shadowgems sell for 3g per and Moss Agate's are 1g 50s per. Wool cloth is also 5g per stack
So on that run I made
I just made 76g in 9 minutes.14 (Shadowgems)x3(gold) 42g
6(Moss Agate)x1g50s = 9g
5 (stacks of wool cloth)x5g per stack = 25g
This doesnt even consider the greens that some of the most valuable twink items also drop there. Peice of advice also sell all decent weapons that give spell damage, strength, agil, stam, or int. Many people leveling alts will easily drop 2g for a green for their lowbie.60 (Minutes in an hour) / 9 (Minutes in a run) = 6.66 total runs per hour
6.66 Runs x ~75g per run = 499g Per hour
Happy farming