Utilization of resources used to provide a service, and/or costs associated with providing system resources for a service, are tracked in a system where the available resources vary depending on a variety of conditions including resource utilization by other users. The methods are well suited for systems such as mobile communications systems, where the amount of resources and/or costs to a system of providing a service are dynamic and can change on a relatively rapid time scale. Resource utilization is tracked on a per subscriber basis. Service charges can be determined as a function of both the amount of resources consumed and the amount of data delivered, with the amount of resources being used to deliver a fixed amount of data units varying as a function of environmental and/or other conditions. Service charges are sometimes determined as a function of the impact of providing the service to a first user on other system users.