I assume that your sensor has worn down, triggering the warning light. First thing to do is determine whether it is front or rear, then determine how much more pad thickness you have on the other set. Then decide whether you are going to do both front or rear, or just the set that tripped the sensor. Then decide whether you need to install new rotors, or just pads. Then decide whether you want to shop the internet for parts or let the installer use what they want and charge you accordingly. Then decide whether you want to use your trusted local garage mechanic, or go Mini-specific independent like Mach V or PTuning.
Lots of opportunities to save money in the process, but $1500+ is insane.