The alchemy system is designed for those players have strong demand for Gold. As we know, gold is used for skill enhancement, gear, and so many aspects. The gold acquirement from game itself might be probably not enough.
Players can take a free chance to make gold every day. After that, 200 diamonds will be cost to change 20000 gold for each time. There is also come possibility for players to obtain additional gold from 2 to 10 times of the original 20000, which means that we can acquire 10 times gold with only 200 blue diamonds.