Lol sometimes I wonder how you reason, we're brainstorming on possible solution to increase the payrate for campaigns which will also encourage quality contributions just as merit have, as participants tends to put in more efforts into their style of writing when there's a motivator (e.g to retain their spot in campaign, pass on a vital information or get some merits). Currently I feel the signature participants are been treated as salves, the payrate wity requirements associated with most signature campaigns aren't encouraging.
I have regretted the opportunity of managing a campaign just because of the poor payrate the campaign insisted on paying (and now the campaign is been managed by someone else on the forum). There's no minimum payrate simply because the forum doesn't moderate signature campaign and nothing else. Also i wasn't asking them (the forum) to moderate, just recommending the campaign managers put heads together to workout some strategy to keep the signature industry fair for the participants.
I agree with some of your thoughts, some campaigns pay very little compared to others, although they are looking for very high criteria. If we look pay rates for Legendary members, most campaigns pay up to $100 per week, and that is good amount in some countries. But some lower ranks are getting only dust ($5 for Member rank), which really could be classified as a category of modern slavery.
Some would say that no one is forcing anyone to join the signature campaign, but users just take what is offered. I think campaign mangers can affect owners of promoted services in a way to set higher prices for all ranks and to stop forcing min amount of post per week. But as you may indicate from your own example, there will always be those who agree to all conditions asked by service owners.
This is the current situation with signatures campaigns :
https://bitcointalk.org/index.php?topic=615953.1340