"From there you can set # of allowed nodes to create, expiration, etc."

and probably set the type of nodes (content type) they are allowed to create... But say if I were a user and I purchase a Product Creator Role (say story) so I am set to create 1 story node. After that what will happen to the role, will it just be back to default user role...and then they purchase another Creator Role to create another node? If they purchase multiple nodes, how will it know which type of nodes if it's based on roles?

Also if it is set that someone can create 5 allowed nodes, would they all be the same type of nodes since it would likely be hard to distinguish one type from another if it's based on role?

Sorry if this is confusing or I'm just confusing myself now. I think I might take a look into pay per node by ecommerce also to see how it's really working. But the idea of paying per node will be more clear as to exactly what type of node it will be that they are paying for.