Bounty campaign is a good way for projects to spread the word and gain publicity in the cryptocurrency market. But it is not the best way to gain investors. Good projects don't depend on bounties alone to promote their token sale.
And this is because when bounty hunters post about a project, majority of these posts is only seen by other bounty hunters and not to the real investors. And these posts are just basic and can not convince good investors to invest.
Bringing in the investors and funds depends on the team's marketing ability and their ability to close deals. This is why good projects attend a lot of crypto events and network with people.
Though bounties help a project to create popularity and hype among crypto users, the main investment and funds is brought in by the team's marketing and closing ability.
Maybe you suppose that real investors are who have lots of money and bounty programs can not reach out of them, but in my opinion, every person in this market including bounty hunters all may be investors of that project if they realize that it is really good and have many potentials. And when bounty hunters do their tasks such as share post or link about project, their friend may also become a investor like them as well.