This estimation doesn’t account for server maintenance costs and it’s more of a cost from a user point of view, and yes, users pay for their searches.
How does Google gains money from user searches?
It’s simple, through AdWords! This is the google component in charge with commercial broadcast through partner websites and search engine.
How much do we pay for a google search?
In 2011 AdWords generated income of more than 36.531.000.000 $. During this time a number of 1.722.071.000.000 searches were made. By simple calculations we see that a google search costs no more than 0.02 $, therefore 2 cents.
|Year||Searches||Ad revenue||Price per search|
That means that users watched with every search commercials of a mean value of 3 cents in 2014.
Another approach can be found here : http://news.bbc.co.uk/2/hi/7823387.stm
Everything described above is a guesstimation made by myself.
Image source: http://www.edge-online.org/tips-to-use-google-search-in-the-right-and-efficient-way/