300k+ an hour by farming Core of Arreat over and over again. Yes, you will be driven insane by the end of an hour's worth of runs.
But this beats the heck out of powerleveling for gold and can be a nice break from flipping on the auctionhouse.
Required Stats (refer to image below):
200% Gold Find, the more the better your income
25% Movement speed, 15% from gear and 10% from passive
Gold Pickup Radius 40+, found on the same gear as your gold find
Gear:
Skills:
Optional:
You can take a follower with full gold find gear, and 20% of the follower's gold find is added to your total.
Disclaimer:
This guide and farming area is for ALL classes, but I only play Monk so I can't say which abilities are best for the fastest farming on other classes.