Amazon Sns and cloudwatch pricing

Im studing aws pricing and I have two doubts about Amazon SNS and Amazon Cloudwatch.

About cloudwatch, Im using it to monitor sns topics and to monitor a dynamodb table. Im reading about cloudwatch pricing and it says that the basic monitoring metrics for amazon ec2, amazon ebs, elastic load balancers and amazon rds are free. So to monitor sns topics and dynamodb its not basic monitoring and we need to pay $0.50 per month for each metric?

About SNS it says that we pay based on the number of notifications we publish, the number of notifications we deliver, and any additional API calls for managing topics and subscriptions. Im bit confuse about this pricing, we pay for any API call, for example create a new topic, getl all topics, etc, ok this part it is clear, but Im not understanding about the other two, for exmaple in my code I have :

message = "this is a test"
message_subject = "Message test"        
publication = sns.publish(topicArn, message, subject=message_subject)

In this case we have the cost about publish, and also in this sns.publish we need to pay relative to API calls? And also we need to pay when we publish a message, and to this cost it is added the cost of deliver notifications? But its not the same thing? Publish a message or deliver a notification? Or notifications it is that confirmation subscriptions that we receive in email when we subscribe some email in the topic?

subscriptionEmail = sns.subscribe(topicArn, "email", email)