With the maturity of Cloud computing comes research into converting a range of traditionally best effort programs into cloud-enabled services. One such service currently under investigation in the Elastic Media Distribution (EMD) project, is how to enable qualitative, reliable and scalable realtime media collaboration services using proven Cloud technology. While existing best-effort solutions provide plenty of features, they do not provide the quality guarantees and reliability required for critical services in globally distributed corporations. On the other hand, some pricey dedicated solutions do offer these low-delay, reliable cooperation services, but without the benefits that clouds can bring in terms of scalability. In this paper we describe results attained in the EMD project on novel resource provisioning algorithms for a mixture of end-to-end Audio/Video streams with file-based transfers, allowing for configurable tradeoffs between service response time and cost. We extended the CloudSim simulator with models allowing us to simulate collaborative interactive sessions (more specifically educational real-time collaboration), and evaluated the performance of our proposed provisioning heuristics. The results show that the proposed dynamic algorithm allows for automated cost-performance tradeoff by reducing average total Virtual Machine (VM) cost by a maximum of 58% compared to more naive approaches, while keeping average time for clients to join a meeting in line.