AWS Lambdas and step functions in java

I am looking to implement AWS step functions ( lambda) in java.. Wanted to implement kind of POC ... Step functions need to read data from table(Aurora / DynamoDB) and process some logic ( like conditional based checks) and update the data back to Database at the end of step function cycle... Let me know what is the cost / hours for this task

Take an example as Student / employee data stored in table and we read that using lambda and 2nd lambda process some logic (conditions like student age < 20 , his score in math >80 certain logic) if score is less than 70 certain logic ... etc .... then finally store data back to database thorough a lambda and write some message into SQS/SNS

Thanks
P