This paper presents payoff allocation for PSS control service in the restructured power systems. The method is based on cooperative game theory by using the Shapley value concept. Because of the complexity and difficulty associated with the system dynamic performance of the PSS to a financial cost, ITAE performance index is used to evaluate the contribution of the PSS for increasing system stability and it's worth allocation. A three machine power system has been used to illustrate the effectiveness of the proposed technique and the variable payoff shares for the generators under various load conditions. A realistic scenario represented by a daily load curve is also considered to demonstrate how loading conditions affect the payment for the generators. The simulation results show that the proposed methodology provides fair and economically efficient prices for the contribution of each PSS in the stability enhancement of the power systems.