A practical pricing mechanism is the foundation for the deploying of IP multicast in the inter-domain Internet. The IP multicast service model and its pricing mechanism are discussed in this paper, by considering the motivations of different partners in the process. Three models are proposed for all applications in the real environments. They are ICP-USER model, ICP-ISP model and ICP-ISP-USER model. In every model, the applied scenarios, resolving method and the complexity of algorithm are described. Here, the Internet is considered as an ecosystem. So the work embodies the self-organization property of the Internet based on the game theory, and respects every role's right and benefit, which is good at the health and stable development of the Internet. So it has great practical feature.