Different from unicast data delivery through dedicated channels, next generation Multicast and Broadcast Service (MBS) delivers data with higher bandwidth efficiency through multicasting. When a group of online users receive the same MBS content, the average MBS network cost per user can be significantly reduced. However, traditional charging methods are unable to account for the variation of network resource. To address this shortfall, this paper develops an innovative concept in MBS charging to realize the goal that "the more users join an MBS session, the more everyone saves." Specifically, we propose a multi-tariff charging method for MBS with a competitive advantage that attracts more users to subscribe to MBS services. Analysis and numerical results demonstrate that operators can alleviate customer concerns about user credit consumption with dynamic tariff while remaining profitable in MBS. These features in our multi-tariff charging method can create a "win-win" situation for both operators and subscribers.