I own free directory and I put some work in it. This is why I want to earn something with it. First i have tried with TLA affiliate program but I didn't earn any money. Than I put adsense on my directory. I read on some forums you can't earn anything from adsense on your directory but I have decided to try it. And I'm happy about my decision. I run AdSense on my directory for three month and I earn more and more every month. Yesterday I earned 2.2$. I just want you to know you can earn something with your directory.
I was going to add Adsense on my directory too but actually I think it will decrease it's quality. My directory is a premium paid web directory with deeplinks and if I place Adsense ads on it I think I'm going to sell les links. Instead of trying TLA to sell links on your directory, sell them directly here on DP in the link sale section. I had great results by doing so
The problem with running AdSense on directories is that they are visited 99% from webmasters. That's why the earnings are low.
In addition to what has been said. My findings are that in general AdSense performs poorly on directories. It performs particularly poorly on general directories (it is not necessarily a case of paid vs. free.). However, I have used it on several niche directories and gotten better results (still relatively low CTR of ~0.5 to 1%) but anything from 75c to $2 per click.)