The method Blacklung used is not cheating or some kind of a bug. The players used the unique and tricky method of fast leveling based on the gold farming. Of course, a lot of preparation was done, so it won't work as your everyday method of fast leveling. The idea behind the method is you receive insane amounts of experience by picking up gold. For that to happen you need these bracers. Apart from magical bracers you would also like to have various enhancers of gold drop rate. For example, as you can see in the video, the player has a 600+ paragon level. It allows him to boost his gold drop rate with the help of paragon points.