After you remove load balancers and Elastic Load Balancing environments, you can stop or terminate Amazon EC2 instances. Stopping an instance allows you to start it again later, but you might be charged for storage.
You might want to refer below links to help you understand better.
Avoiding Unexpected Charges: http://docs.aws.amazon.com/awsaccountbilling/latest/aboutv2/checklistforunwantedcharges.html
According to Amazon’s policy, they don’t charge for hourly usage for a stopped instance, or data transfer fees, but they do charge for the storage for any Amazon EBS volumes. Also, please note that each time you start a stopped instance, they charge a full instance hour, even if you make this transition multiple times within a single hour. If you wish to terminate the instance, please make sure that you delete all of the volumes associated with the instance in order to prevent from incurring charges.
Stop and Start Your Instance:
Amazon EC2 Pricing: