You can save hundreds of dollars by replacing the pads and rotors yourself. And it only requires a few cheap tools.

As the pressurized fluid acts on the caliper piston, it squeezes the disc brake pads against the disc brake rotors. The energy of the pads pushing against the rotor generates heat from friction.

which in turn drive the pistons that force friction material against the wheel hubs, stopping the wheel. The master cylinder is designed to last the life of the car, but like brake calipers ...