Replacing brake pads yourself is cheaper than having a shop replace the brake pads.
When you replace the brake pads yourself you only spend your time and the cost of the brake pads.
You do need some tools such as sockets, ratchets and a caliper compressing tool to compress the caliper piston back in to allow the brake caliper to fit with the new brake pads.
You can buy those tools pretty cheap and if you have a jack, jack stands, and are not afraid to get dirty then replacing the brake pads yourself can save you some money.
There's lots of good videos on YouTube showing how to replace the brake pads yourself and it can be down within an hour or less.
Brake pads cost between $15.00 to $50.00 per set depending on the make and model of vehicle.
If your brake rotors are bad then you also need to replace the brake rotors especially if they are really rusty, thin, glazed, cracked etc.
I replace my brake rotors along with my brake pads every 2nd set of brake pads as it's just as easy to replace the brake rotors then as well.
I buy my brake pads and brake rotors online through Ebay which saves me money.