It depends on the rank of your account on bitcointalk, obviously higher rank means higher earning due to the payout being higher
Looks like YoBit pays the highest. I'd be happy with 0.03 BTC / month posting here and there to be honest!
I don't think that 0.03 BTC / month pretty good money. I expect a little more, it's about 0.1BTC/MONTH than I could be satisfied. Yes, It depends on your rank obviously, but also important that what service you have promoted.
You're spoiled. If there were no better paying campaigns and all you could get was 0.03 a month you'd be posting for it without second thoughts.
What you're getting here is basically free money, because you would be on the forum even if there were no campaigns at all and if you are here only for those campaigns you should find a better source of income. The forum doesn't need you.