To forecast your costs, use the AWS Cost Explorer. Use cost allocation tags to divide your resources into groups, and then estimate the costs for each group.
Reference:
https://aws.amazon.com/premiumsupport/knowledge-center/estimating-aws-resource-costs/

Elastic Load Balancing supports the following types of load balancers: Application Load Balancers, Network Load Balancers, and Classic Load Balancers. Amazon ECS services can use either type of load balancer.
Application Load Balancers are used to route HTTP/HTTPS (or Layer 7) traffic. Network Load Balancers and Classic Load Balancers are used to route TCP (or Layer 4) traffic.
Reference: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/load-balancer-types.html

Reference: https://wa.aws.amazon.com/wat.concept.elasticity.en.html