I don't pay that much for this stuff either but that is what these places are asking for it. For example page 72 of the current Truck Shop catalogue, 5 lug disc brake kit with booster, $699. If you can get parts from a 74 Malibu doner car like I did, buy the brackets, booster & MC, you can reduce the price considerably. There are many ways to arrive at the desired result, a person just has to figure out what fits their needs.
Fred