looking at that add the e34 price might not be so bad... but I have no idea what the components go for maybe:
engine R 12k
Gearbox R 4k
prop R 2k
drive shafts R 2k
diff R 2k
steering? R 2k
Brakes? 4k
other bits?
the list above is already getting close to 30k and im sure there are bits missing maybe offer 20k and see if you can get it for 25k