2% is fine to start with. I believe that's the average on most of my sites. You should work on your ads to get higher though.
Want to know more about adsense.........just click here..........by the way ill add more content to it in a day or two. Hope this will help you SEO for Adsense.
The higher your CTR is, the less you'll eventually pay for your clicks. Google considers the Quality Score of your keyword that includes CTR. You know, Google is interested in those ads that attract visitors. There are certain ways to raise your CTR, you can read this article for more info: http://www.semrush.com/blog/articles/click-through-rate-ctr-importance-for-seo-and-ppc-article/
Pay for clicks? I think you have missed the point that he's talking about adsense CTR and not adwords CTR, so he's not paying for any clicks.....
2% is ok with sites with lot of good content. Sites with less content and no other links but adsense ads get more ctr.