Smart Pricing is Google's attempt to protect advertisers through their Google AdWords program which will automatically lower the CPC (Cost per Click) of an AdSense ad if Google think the publisher gives low conversion rate for the Google AdWords advertisers. This means that if an AdWords advertiser bids $1 on a keyword, you as an AdSense publisher might get a lot less than that $1 per click.
If you think you are earning too little per clicks, you might be smart-priced too. You may want to review the following suggestions to fix this situation.
Smart pricing generally affect low quality sites as they don't normally attract quality traffic which in turn doesn't give good conversion to the advertisers. This is normally true for sites on video, games or wallpaper sites. You have the option to either improve the quality of your site (and attract quality visitors), or change to a new niche altogether.
If you're running multiple sites, and one of them is causing you to be smart-priced, consider using separate AdSense account for the low quality site. This is because smart pricing affects your entire account, and not just site-specific.
If your site has a number of ad units placed all over your sites, you might want to reduce it a bit. This is to make sure there are less accidental clicks from your site's visitors which doesn't give good conversion rate for the advertisers.
If there's nothing you can do about your site, or you just don't want to, you can just opt for other advertising options such as Chitika or Nuffnang. You can also monetize your site using affiliate programs.