Elastic Beanstalk itself is free of cost. You only incur costs for the EC2 instances or load balancers you're running with it. The platform itself is completely free.
Platform-as-a-service (PaaS) is a kind of cloud computing service in which, rather than having to build and maintain their own infrastructure, a client is able to develop, run, and manage applications on a platform that is provided by a third-party provider. The provider hosts both software and hardware, freeing the client from having to install and handle them in-house.
Elastic Beanstalk itself is free of cost. You only incur costs for the EC2 instances or load balancers you're running with it. The platform itself is completely free.