A fair bit , I bought my calipers at a good price from gumtree but had to paint them myself and then messed about with the other bits, in the end it came in at a few pounds over £500 , I doubt very much you will get it done any cheaper chap, maybe if you shop around and get some used calipers that need refurbing but then you will need to get them refurbed which will cancel out the savings.
I have seen a few used kits for sale that were in good cond but were still over £500 and the discs were used etc.
But they are epic brakes compared to the standard setup.