1. A method comprising: receiving, by a virtual appliance monitor executing in a network cloud system, appliance state information representing an execution state of a virtual appliance of a set of virtual appliances instantiated in the network cloud system that the virtual appliance monitor is to monitor, wherein the virtual appliance monitor is instantiated by a cloud management server device managing the network cloud system; managing, by the virtual appliance monitor, the set of virtual appliances in view of the receiving appliance state information; and terminating, by the cloud management server device, the virtual appliance monitor and the set of virtual appliances monitored by the virtual appliance monitor when a subscription period for the virtual appliance monitor and the set of virtual appliances expires.