I saw only one member earned 0.005BTC+ with 105 posts and he is Hero member. There are many other campaigns which pays more than 0.01BTC for 30 Min post to Hero member.
Each campaign get to make their decisions on what they want to pay and it's up to users to join if they find it good enough, not all campaigns can afford what other big campaigns pay, I was in a campaign as a Member ranked users and earned 0.006
BTC on a weekly basis, meanwhile there are other several campaigns that doesn't even pay Legendary members that much.
The only feedback I can give as well would be that there should be some differences between the pay rates across ranks, and there should be a minimum number of post required weekly so that you don't keep inactive users in the campaign.