Auto Scaling is a free service, however, all ECS instances that Auto Scaling automatically creates, or manually adds, to a scaling group will be charged according to their instance types. Note that you will still be charged for Pay-As-You-Go instances even after you stop them. To avoid further fees, you must release the instances.
Note: In circumstances where there may be insufficient ECS instance inventory, long startup time, or other issues that impact Auto Scaling, the full resources of scaling may not be displayed.