Many people join a lot of bounty. I know some people take 40-60 bounty at the same time. They can earn $ 2000-3000 per month. But I do not know how they set the time. They will probably work 20 hours a day with bounty 
Well i am earning a great amount of money especially when i joined a promising bounty campaign and the last bounty i joined is i almost earn $3k and i am hoping that the current bounty i joined will raised a huge amount of money so i can became more profitable.