I did some research about sig campaigns, now i know that most at the time even legendary members are not earning even 50$ per month, some of them say that they earn 100$, but that's also not interesting for me. I personally would not even waste my time to post for sig campaign every day just to get 50$-100$ at the end of the month.
I think signature campaigns do not pay as much as they used to pay before. One of the reason can be a very high increase in bitcoins price. Another reason might be a lot more people are willing to join the campaigns even at a low pay per post rate.