I'll come back with an answer to you on this soon.

We are currently running Google ads on our site but are doing this for more than just generating sales.

Trigger the mind of Google - does it favour sites that use their Adwords?

We've generated one directory sale since starting campaign!

Could there be a problem with our sales pages - made changes recently to see if can capture the mind of visitors more.

How many clicks - not many so not really costing anything. However, keeping a close eye on this and making changes regularly to see what we can do better.

Thanks Vic. We will look forward to your results

Now i have one google ad on one of my directory's really just to fill the space, it doesnt get many clicks because its at the bottom of the page out of the way, BUT when it does get clicked they are often very good clicks

Most of the directory visitors are web site owners who like to add their link.

they are busy people they just like to add their site and get out.

If you get lot of SE traffic you will get clicks.

on avarage I get $0.06/day on my directories with YPN ads..

I'll give you my view of Google advertisements on a web directory. Since more traffic increases the possibility of clicks, you can figure out that part by yourself.

Free web directories have more traffic than paid web directories do, and you may receive about 200-300 unique visits per day if you have a established free web directory.
30x200=6000 UV's a month assuming you receive 200 uniques per day.
30x300= 9000 UV's a month assuming you receive 300 uniques per day.

This as you may be aware of can bring a quite good amount on Adsense, I've had good results with low traffic web directories, I placed the G ads just below the navigation bar and made it 'less-disturbing'.

Optimize your web directory for SE's and try to target high traffic keywords that may expose your web site and bring you a good amount of traffic.

Meti

I cant see directories making much by way of Google ads.

I have a small directory, and have yet to make anything with Adsense.

Geoserv.

Personally I wouldn't recommend adsense on directories. I own a few good free directories (Yhay.com, kcIndex.com, DirectorySEF.com) which get over 5k uniques monthly. Yhay is getting nearly 9k. I never used adsense on any of them and I never seen any respectable directory using adsense...it just makes the directory to look cheap in my opinion...
I have tried adsense on a ebooks site a couple of years ago and didn't liked so I stoped using it.