It's true that with lower fee, a campaign will certainly not get a higher output or quality output. For example, if we look at Darkstar, Yahoo and Hhampuz, and compare their payrates with others for management, we will see a huge different. Not different in the pay rate, we will see different in the management as well.
However, it's not that as easy as for each projects to pay high amount initially, you know everyone wants least cost with higher output. Projects will try to reduce their cost.
On the other hand, imagine BTC is at ATH. 0.01 BTC = $200 for 25 posts max, I don't think with current rate, much people will be interested to post 25+ in a week (It depends on user too, Royse posts 100+ each week although he is not required to do so).
With ATH rate, a project will be paid a significant amount per week which may bring them loss. Fixing the rate will not get anything better. I think rate isn't something we should account, it's always the campaign manager and users. If CM recruit regular poster, payrate will not make any much different.