Depends on the type of project and the type of service you are providing. Do not expect to make a lot from twitter since a large number of users participate in that. On the other hand, signature campaigns are more rewarding but the downside is that you can only participate in one signature campaign at a time. As per my experience, the earnings per campaign vary from 20$ to 1000$. I have never ever received more than 1000$ from a single project since I started working on the forum, and those 1000$ too were from a long signature campaign. I hope this clears your doubt.
I think it is not certain and it is always changing all the time. Sometimes I can get around 50 dollar in one week. But sometimes I do not get anything in one week. The worst thing that ever happen to me is that I do not earn any money in one month, that is very sad for me, hehaha. I have already use this kind of method to earn btc and eth in order to invest. I do not need to use my salary and my personal saving to invest into btc and eth. And that is a good thing for me. I hope this world of crypto will continue growing, and the world of btctalk will keep growing too, hahaha.
I hope the world of ICO or something like that will keep growing so that the world of bounties and campaign in this forum will growing too. There will be more and more bounties and campaigns that we could work for and a lot of opportunity for us to have. With the ongoing competition and the users in this forum, I kinda afraid and discouraged. I hope I will be fine until I get the correct profit I want to get from btc.