Because keywords are sold through online auctions, prices often spike
for those connected with big breaking-news stories. On the day of the
Virginia Tech shootings, the cost per click of buying phrases such as
"Virginia Tech," "Virginia Tech shooting," and "Virginia Tech massacre"
jumped as high as $5. Over the following week, prices dropped to six or
eight cents a click, according to Reprise Media, a search-marketing
firm owned by Interpublic Group. A longer-lasting news term, such as "Iraq war," costs on average 39 cents a click, Reprise says.
Here is the full story, and thanks to Nick for the pointer.