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.