there seems to be hopes in adsense as people really can earn more than 1k per month. i'm working towards that for now.
My highest was just over 19K with a major drop to about 8k due to some, apparently questionable linking practices and subsequent sandboxing in google. Solved that problem but took about 4 months to start seeing the traffic come back again. How I did it - unique valuable content, unique valuable content, unique valuable content