Update: – I stand corrected… this comes DIRECTLY from google adsense help centre

https://www.google.com/adsense/support/bin/answer.py?hl=en&answer=32859

For displaying ads with AdSense for content, publishers receive 68% of the amount Google collects from advertisers. For AdSense for search, publishers receive 51% of the amount collected from advertisers. These percentages are consistent, regardless of a publisher’s geographic location, and are not in any way averaged between publishers. We don’t disclose the revenue share for other AdSense products; the revenue share varies for other products due to different costs of developing and supporting these products.

We believe our revenue share is extremely competitive. However, revenue shares alone can be misleading, so we encourage you to focus on the total revenue generated for your site. For example, if the Google ads on your site generate $100, with our 68% revenue share you’d receive $68 through AdSense. Another ad network might offer an 80% revenue share, but only collect $50 from advertisers, so you’d receive $40.

With the vast number of advertisers competing to appear on AdSense sites, our system ensures that you’re earning the most possible for every ad impression you receive.

the 68% is misleading. as most of goolges ppc income comes from affiliate partners AOL, ask.com and a few other BIG players. Google doesn’t reveal the size of those contracts, and nor should it as it’s commercially sensitive. My best guess is they pay these folks up to 80% of the search revenue, and for everyone else using adsense they pay somewhere closer to 12.5% – 20%. I can’t figure out the exact amount, but that is my best guess.

Don’t get suckered into thinking you can earn 68% per click on adsense, as it simply is not true.

A well optimised site can get upwards of a 10% Click through rate. (Which is what I get)… once optimised, then it is about generating traffic. The more traffic, the more you earn.

However… rather than flogging a niche it is much better to just write websites about things you’re pationate about. forget about high paying words like insurance, forex, property, banking etc… if you’re pationate about flowers, then write a site about flowers… monetise it, optimise your adsense, and keep blogging or writing pages about the topic you love! – it’s far more rewarding.

my site is http://www.classicspeeches.com if you’re interested to see an example of a site optimised for adsense.

G

I have heard that mid-size website owners on average gets about US$100 – US$300 from AdSense. Not very motivating especially if you are just starting a new site.