With AWS Step Functions, you pay only for what you use. You are charged based on the number of state transitions required to execute your application.
Step Functions pricing details
Step Functions counts a state transition each time a step of your workflow is executed. You are charged for the total number of state transitions across all your state machines, including retries.
The Step Functions free tier includes 4,000 free state transitions per month. All charges are metered daily and billed monthly.
For details, see the Step Functions pricing examples.
State transitions pricing
You may incur additional charges if the operation of your application workflow utilizes other AWS services or transfers data. For example, if your application workflow invokes an AWS Lambda function, you will be billed for each request and for the duration of each Lambda function. For details on AWS service pricing, see the pricing section of the relevant AWS service detail pages. Links to pricing for some of the commonly used services follow.
External data transfers to and from Amazon EC2
Requests and duration
On-Demand, Reserved, and Spot Instances
Fargate and EC2 Launch Types