Why are disc brakes more expensive than drum brakes?

Disc brakes are a common braking system, and when the brake disc rotates, the brake pads in contact with it generate friction. This frictional force will be converted into kinetic energy between the brake disc and the wheel stopping rotation, thereby slowing down or stopping the wheel's rotation. This case established a disc brake and gasket model, and based on the thermal field analysis module of COMSOL software, simulated the heat generation process and temperature field distribution of the brake during the braking process. The simulation results are shown in the figure: