5G legacy communication systems from commercial vendors are 'all-rounders' in terms of performance in that they can support large numbers of nodes with high Quality of Service (QoS), but they are costly. On the contrary, WiFi networks are cheap, but can only support small numbers of nodes with low QoS. Small and medium enterprises (SMEs) typically have only a small set of homogeneous communications use cases, but operate under tight cost constraints. We propose 5G on the Cheap (5G Cheap) as a highly customizable open-source 5G communication system. We describe a range of configuration options for the open-source Core Network (CN) and the Radio Access Network (RAN) for 5G Cheap. A low-end 5G Cheap configuration can serve the specific needs typical SMEs and costs only roughly one tenth of the cost of a commercial 5G legacy system.