CM Pay Per Post (CMPPP) - How To - Create Price/Subscription Options
The price is called a subscription and it allows the user to pay a specific cost for viewing the post for a defined period of time.
How to Set a Price for a Post or a Group of Posts
In the plugin settings you can define several options: create groups and set its pricing.
In the following example, the group "Group 3" has 3 subscription tiers.