I earn about 5% of content ads But due to google search just available in my country language, so I expect to get it mor than nowadays
Looks like it got buried, but Cormacs reply is I think, a better way to approach things: Its a good earner for me. Dont use the Search within the Adsense CP. Create a Google custom search engine and add your adsense id. Also add the url of your site to the new search engine, if you have more than one site enter them too. The more niche related sites you have the better. Create a results page using a header & footer. Tell Google the new url and they'll give you two pieces of code, the search box and the search results. Best place to slap the search box is directly below your content. I usually place it after the last paragraph. Fire up the search engine and now you have your own internal search engine that can make more money. If you have some content sites and some money sites, this can be a good way to push some traffic between them too & it'll generate more revenue than adsense search. It's a real network effect. the more sites you have the more $$ you can generate w/ custom search.
Thats it exactly Pleb and bottom line comes down to how much traffic you can actually push via the network of sites.