AWS cost during emr creating&bootstrapping

Per "Q: When does billing of my Amazon EMR cluster begin and end?" under https://aws.amazon.com/emr/faqs/?nc=sn&loc=5, Amazon EMR billing commences when the cluster is ready to execute steps. Amazon EMR billing ends when you request to shut down the cluster. For more details on when Amazon EC2 begins and ends billing, please refer to the Amazon EC2 Billing FAQ.

There is also EC2 billing in addition to EMR which starts when Amazon EC2 initiates the boot sequence of an AMI instance per "Q: When does billing of my Amazon EC2 systems begin and end?" under https://aws.amazon.com/ec2/faqs/#Billing