The new quality based pricing system being rolled out by Yahoo will allow advertisers to enjoy reduced click charges based on ad relevance and quality.
Yahoo announced in a mass mail out yesterday the launch of Quality Based Pricing. Discounts will be automatically applied to an advertisers account based on conversion rates and other measures. The roll out of the system has already begun as of yesterday.
There is nothing you need to do to receive this discount, simply continue creating quality relevant ads for your campaign, and assuming the quality is high enough you will start to see some reduced costs.
For more information visit the Yahoo Search Marketing Help page for Quality Based Pricing.