Have 3 year old "shopping comparison" website. (Bizrate connected)
Site has thousands of internal links and a couple dozen inbound links. Yet even with this low traffic I still make about $5 / mo.
Google figured out long ago that it was a shopping comparison site and devalued it to the point where it gets only about 50 impressions a day (verified by webmaster tools). It had been this way for over a year.
Had written the site off for dead then I decided what the heck, and put some adsense code in.
Two days later - Google started giving the site traffic. Over the next week - it got 15,000 impressions. Quality score (as reflected by conversion rate) increased as well. (ie: % actually increased) I earned $25 from the store and another $15 from Google that week. Alone.
After a week - Google then slowly reduced the impressions back to it's "normal" rate of 50 impressions per day. (Took about another week). Now site is dead again.
What this prooves ....
1. That adsense code does help. At least for a short period of time on sites that have existed for a while before code was installed.
2. That quality and conversion rate actually improves with impressions. (ie. percentage increase. not just one for one. This explains how high traffic sites have higher conversion rates (by %) than low traffic sites.
3. That Google (not you) is in control of the success of your website. The increase in conversion means that this site IS relevant and useful. It is Google who has determined that comparrison sites are of no value. (Unless you are Bizrate or Shopzilla and spend millions to buy Google juice.)
The game is rigged folks - whether you want to admit it or not.