Answer:
Different parts cost different amounts. It depends on the type of coaster as well. Is it wooden, metal, suspension, etc? It also depends on the speed of the coaster, as a slower coaster might not need as durable material.
Prices for brakes verses chains verses supports will all be priced differently based on many many factors. Even a small kiddie coaster might cost a few thousand for all the parts, but your best off for a real estimate would be to talk to a manufacturing company who produces parts for coasters.