In wide area monitoring system, phasor measurement units (PMUs) plays a vital role in providing synchronized measurements with the help of Global Positioning System (GPS). In conventional optimal PMU placement methodology these PMUs are placed optimally across the power system network ensuring completely observable. It is found in literature, that most of them neglect the PMU channel limitations, variable PMU costs, and measurement redundancy improvement. To address this problem, in the present paper an optimal PMU problem is addressed by optimizing the two objective functions that are conflicting in nature, namely, minimization of PMU installation cost and maximization of measurement redundancy at the same time. In order to allocate PMUs, both channel limitation and variable cost of PMUs has been considered. A non-dominated sorting genetic algorithm-II (NSGA-II) based methodology is proposed to solve the combinatorial optimization problem. The Pareto optimal solution obtained using the concept of crowding distance and non-dominated sorting. A multi-criteria decision making technique based on VIKOR method is utilized for finding the best compromise solution from the set of Pareto-optimal solution obtained through NSGA-II. To verify the effectiveness and reliability, the proposed approach is tested on IEEE 14-bus, 30-bus, and 57-bus systems.