From what I can tell, yearly Search ad revenue is in the neighborhood of $104 billion [0], and the number of yearly searches served by Google is somewhere in the neighborhood of 3.1 trillion [1]. This brings the revenue per search to somewhere between 3 and 3.5 cents.
[0] https://abc.xyz/investor/static/pdf/20210203_alphabet_10K.pd... (page 33)
[1] https://www.oberlo.com/blog/google-search-statistics