It is really depends on the person or the bounty hunter. Some bounty hunters are doing this on there spare time justbto add additional income on there daily life or some are doing these for a start for their portfolio. They keep on joining bounty campaign to stablish a good portfolio to start trading. Some bounty campaign give enough tokens to start to buy ethereum or bitcoin or other altcoins in the market. But some are doing bounty campaign as their bread and butter.