AdSense help doesn't really say anything (that I know of) about smart
pricing, however, in the AdWords help you will find the following:
"Google's smart pricing feature automatically adjusts the cost of a
keyword-targeted content click based on its effectiveness compared to a
search click. So if our data shows that a click from a content page is
less likely to turn into actionable business results - such as online
sales, registrations, phone calls or newsletter signups - we reduce the
price you pay for that click. With no extra effort for you, Google
technology helps ensure you get strong ROI from your AdWords
advertising, wherever your ads appear."
If the advertiser pays less, the publisher/owner of the site on which
the ad appeared earns less.