Mobile ad hoc and sensor networks often contain a mixture of nodes, some of which may be selfish and non-cooperative in providing network services such as forwarding packets in order to conserve energy. Existing trust management protocols for mobile ad hoc networks (MANETs) advocate isolating selfish nodes as soon as they are detected. Further, altruistic behaviors are encouraged with incentive mechanisms. In this paper, we propose and analyze a trust management protocol based on the demand and pricing theory for managing group communication systems where system survivability is highly critical to mission execution. Rather than always encouraging altruistic behaviors, we consider the tradeoff between a node's individual welfare (e.g., saving energy for survivability) versus global welfare (e.g., providing service availability) and identify the best design condition so that the system lifetime is maximized while the mission requirements are satisfied.