Participating in a bounty is a kind of investing. Bounty hunters buy investments for their time. Otherwise, they could earning the money for which they bought tokens.
Bounty Hunter is also a job. People promote projects and do it for tokens and not for real money. The only disadvantage of this work for the money for it you can get in half a year or even a year
Time is money, promotion of the project is also work and the project rewards people, everything is fair.
The project itself is interested in attracting new investors and disseminating information, so the work of bounty hunters is valued and paid fairly profitably.