Imagine how much all those computers would cost though. Even if they were all used and old(in which case a lot of bots couldn't be ran on them) it would still take a while to pay them off. You also have to pay the people making sure bots don't malfunction, check to make sure computers aren't having problems, etc. Gold is priced at .65 per mill(?) and estimating that green dragon bots can make 400k per hour, then you're making ~$.30 per bot per hour. Looking at the pics they have ATLEAST 100 computers which are all running 8(# from the screens on the first pic) per computer. 800 bots making $.30 per hour is $240 per hour. You have to pay the electricity bills, price of the computers(would take a long time to pay off), and the people who manage the bots. Even though they probably have 300+ computers at this place, I doubt it's good cash compared to what people in the US/UK make on average. I don't know the average wages in China so I could be completely wrong about everything in this post(may be great money in that part of the world). Instead of buying computers, renting lots of vps or dedis could work.