I believe that the bounty hunters who are over jr. member should get a better pay since that the merits are not easy to gain. I believe the heros and legendary worth far more than 100 u / week. While since the marketing price and ICO, it is hard to redeem at the ideal price. That makes life hard.
You seems to be new around here (but strange that you already know about bounty, rewards and etc). How much do you think Hero/Legendary should earn for 15-25 posts? Take a look what kinds of quality these high ranked member post here. Sometimes I think that don't deserve payment at all.
Try to find statistics of people ranking-up. There are plenty of people who went from Newbie to Legendary after merit system appeared on the forum. So everything is achievable.