1k = $1.61USD atm, Like Max stated, depends how much you farm a day and how much you AH in 4-7days. When I first started I bought 10k, and flipped that into about 150k working the AH(Very time consuming), But I then turned that 150k intol almost 1mill in 2 weeks. So it depends how much you do. The more gold you sell in bulk, the more $$$ you lose out on. Say you sell 5k to 20 different people, you'll get more money that way instead of selling 100k to one person. Gold farmers do not have a set price, they take anywhere from 5%-20% loss if they use the Chinese farmers and websites they sell to. But everyone has their own methods. I sell to my friends list and do pretty good every month. $1000-$1500 extra a month is always nice, get to pay more bills off haha.
Just keep an eye on the prices, one day 1k could sell for $1.90 and lets say about 7 hours passes, it could either drop to $1.50 and the discounts on top of that are crazy. I always get my friends about 20% free as well. So it's all up to you, but you can get some decent cash in return.
GL.