The Amazon instances are classified into six families namely Standard, Micro, High-Memory, High-CPU, Cluster Compute, and Cluster GPU.
Basically, configuring an instance within an Amazon EC2 Region and monitoring that instance is a paid service i.e., you pay charges for both configuring an instance in the Amazon EC2 cloud based on your requirement and collecting metrics from that particular instance. The payment varies according to the instance types and the Region in which the instance is deployed.
For more detailed information regarding the Amazon EC2 purchasing options refer http://aws.amazon.com/ec2/purchasing-options/
For more details regarding the pricing of the Amazon EC2 instances based on the Regions where they are deployed, refer http://aws.amazon.com/ec2/pricing/