Spectrum combining refers to utilizing multiple types of spectrum authorization options for a wireless network. The approach is considered as an essential ingredient of high-capacity provision in the coming years. This paper presents a techno-economic framework to analyze capacity and cost of different spectrum combining options. We focus on indoor environments where the traffic demand is expected to be extremely demanding. We describe various spectrum options such as licence-exempt, light licensing, and licensed shared access (LSA). Then, we compare various combinations of these options with increasing traffic demand over time. In terms of capacity provisioning, this framework is based on the idea that spectrum combining must be done at the right time, that is when the existing deployment can no longer satisfy capacity demand. For the cost analysis, most relevant cost drivers are included in a cost structure which becomes the backbone of this framework. The proposed framework can help network providers determine the most cost-effective spectrum acquisition strategy which can meet capacity demand in indoor environments.