It varies A LOT. I have some sites that primarily monetize with adsense, and some that don't. I have some sites that mainly draw traffic from image searches, and some that don't. But.... I have sites with a ctr as low as just over 1%, and others with a consistent ctr in the 7% range.
i didn't put any ads on this site because its a very small site. i have so many other site and my CTR is up to 10%.
He's obviously lying. Don't be so naive. Unless the site is completely full of Adsense with nothing else, it's not even near 10%.
But 10% is not a good rate, I think 5% is the best CTR for adsense. Otherwise our adsense account in a trouble.
My CTR is under 1%, it's a forum site though and most of my traffic comes from image searches - not many clicks for those two categories.