The hybrid energy storage system composed of power-type and energy-type storage possesses advantages in both power and energy, rendering it suitable for various application scenarios. To capitalize on the cost benefits of this hybrid system throughout its lifecycle, this paper explores the optimal configuration of hybrid energy storage systems comprising supercapacitors and lithium batteries for primary frequency regulation applications. Firstly, the cost model of the hybrid energy storage system is analyzed, and a calculation method for supercapacitor costs is introduced to enhance the accuracy of cost estimations for supercapacitor-based storage. Secondly, the lifespan model of the hybrid energy storage system is examined, and subsequently, the cost of battery cell replacement during its lifecycle is computed. Thirdly, the revenue model of energy storage in primary frequency regulation applications is scrutinized. With the aim of maximizing net revenue, the optimal configuration of the hybrid energy storage system is determined. Low-pass filtering algorithm is utilized for power allocation between the different types of energy storage during simulated operation. Finally, a simulation analysis is conducted using actual frequency data of a certain grid, and the results indicate that the application of hybrid energy storage in primary frequency regulation exhibits superior economic performance compared to single-type energy storage systems.