Doing a bounty on the blanket bounties is not doing it for nothing, they do pay. It's pretty much the standard pay until big prizes show up with specific bounties on them, it's not everyday they pop up on the scanner but it's really nice when they do, then there is still the challenge of being able to collect and the paperwork afterwards along with the carpal tunnel syndrome that comes from that PrtSc button.
Now as for the size of the payouts in a blanket bounty that's for another topic specifically but not one that's gonna really budge either. The low pay of a blanket bounty is good as is, as well, otherwise the rise of BH's would be heavy indeed. Even then, not every faction can afford to fork out millions and millions weekly in order to satisfy the RP of bounty hunters yet a measure is appreciated so that we can follow our RP.