Amazon is pushing its serch tool a9 by giving discounts to its users on Amazon.com. Active users get π/2% discount for their purchases. Amazon.com: What is the A9 Instant Reward?.
Sponsored links revenue — from the small text-based ads on A9.com and Amazon.com search results pages — will help offset costs we incur through the Instant Reward promotion. With our automatic π/2% Instant Reward, we are effectively sharing with you some of the money we collect from sponsored links, i.e. sharing the pi.