Also the 0.68 cents is cost of search-related revenues divided by number of searches. However, presumably there are only revenues when someone clicks on an ad

Also the 0.68 cents is cost of search-related revenues divided by number of searches. However, presumably there are only revenues when someone clicks on an ad on the search results page. So a more accurate number would also factor in the ratio of ad clicks to searches. If there's one ad click per 10 pages on average, these numbers are off by an order of magnitude.