Just found some on the internet. I can’t find any proof of this information, but I think the data is quite real. So, I will show you keywords with top cpc, and top google cost per month.
Google.Adsense TOP by Google Cost

Keyword
Avg. Google Searches/Month
Google CPC
Google Cost/Month

auto insurance quotes
9,140,000
$34.59
$3,161,526.00

refinancing
11,100,000
$33.19
$3,684,090.00

auto quotes
9,140,000
$32.69
$2,987,866.00

mortgage refinancing
9,140,000
$32.54
$2,974,156.00

refinancing mortgage
9,140,000
$32.54
$2,974,156.00

auto insurance
24,900,000
$32.46
$8,082,540.00

home mortgage refinancing
9,140,000
$31.23
$2,854,422.00

home refinancing
9,140,000
$31.03
$2,836,142.00

insurance quotes
20,400,000
$29.79
$6,077,160.00

quotes
83,100,000
$25.80
$21,439,800.00

free [...]