Announcing CloudWatch Metrics Price Reduction and New Volume-Based Pricing Tiers

We are reducing the base price of CloudWatch Metrics from $0.50 per metric per month to $0.30 per metric per month, a 40% reduction in price. In addition, we are introducing new volume-based tiered pricing with even lower prices per metric, with savings up to 96%. These will take effect in all regions beginning December 1, 2016.  
Quelle: aws.amazon.com