The most important word here is related. Don’t add content pages about Viagra to your website which is themed around motorcycles just because the average CPC for Viagra is very high. Instead do one of these two things:
1. Type your primary keyword, in this example, "motorcycle"
2. into Keyword Country, wait for the results to appear and then click on CPC. This will arrange all the related keywords by their CPC value bringing the most profitable to the top. I did this and found that -
“Motorcycle Insurance In Michigan” has an average CPC of $10.25“Motorcycle Insurance” has an average CPC of $4.28
“Motorcycle Loan” has an average CPC of $3.34
These are very high average CPCs for which you could develop new content. These content pages would generate higher cost per click Adsense ads from your visitors.
2. Your second option is to type in keywords which are related to your principal topic. Continuing with the motorcycle theme you could type in Harley-Davidson a popular manufacturer of motorcycles. The results show that “Harley Davidson Boots” has an average CPC of $0.84. You could build a page today pre-selling Harley Davidson Boots and generate a nice Adsense stream from that page. Another extension would be the keyword “chopper”, a popular type of motorcycle enhanced by the big shows of the last few years. On Keyword Country a search for chopper brings up related keywords like West Coast Choppers, a famous chopper builder which has an average CPC of $0.95 – again a page or several pages around this topic would be a nice addition to a motorcycle based website.