It depends how big or a little your profit it the end. If the bounty project become successful then you will be paid more than you expexted. But if the bounty project didnt reach your required cap then maybe you will be paid enough on what youve done.
It is true that bounty is absolutely profitable, but the profit is really not fix. I do agree that it is base on the result in the end of the campaign. Some other successful bounty gives bonuses for their campaign participants in way of giving thanks to them for their help and effort to promote their bounty to reach their success. Even if some bounty campaign that are not succeeded, they do paid the specific allocation amount to the participants as their payment for the task or work they done.