Google is the world's biggest, and most valuable search engine (it's currently valued at approximately $90 billion USD), and it's earned the bulk of it's profits from its proprietary online advertising service, Google AdWords.
Google makes billions of dollars each year selling customized advertising that's targeted through their complex search engine algorithms which match internet users with ads that promote products and services they're searching for.
AdWords operates on a bidding system - that means advertisers compete against each other to secure the exact placement of their ads on search engine results pages (SERPs), and even whether or not their ads will appear at all. The more prominently and frequently an advertisement is displayed, the more conversions that ad will achieve for the business - that's what drives up the cost of keywords.
According to WordStream, as of December 2017, these were the top 20 most expensive keywords in Google AdWords Advertising:
Business Services - $58.64
Bail Bonds - $58.48
Casino - $55.48
Lawyer - $54.86
Asset Management - $49.86
Insurance - $48.41
Cash Services and Payday Loans - $48.18
Cleanup and Restoration Services - $47.61
Degree - $47.61
Medical Coding Services - $46.84
Rehab - $46.14
Psychic - $43.78
Timeshare - $42.13
HVAC Software - $41.24
Business Software - $41.12
Medical Needs - $40.73
Loans - $40.69
Plumber - $39.19
Termites - $38.88
Pest Control - $38.84
While the list of most-expensive keywords on Google search tends to shift slightly each year, in general, the focus of the keywords is around solving urgent problems or needs. For example, if someone is searching for a 'bail bond', chances are good they're looking for help right away - that means they'll be inclined to choose the first advertiser that pops up on their Google search results page.
