No Frikkie,
You cant buy a second hand BMW diesel with such insane high mileage, the turbo is designed to explode at 120,000km and then you are going to spend R230,000 to have the turbo fixed...
(You do notice the large amount of sarcasm I hope)
(Seriously though, nice car, I too think its a tad steep and your going to loose if you trade it in, over him 140k, see what he does, remember for some unkown reason you cannot give a BMW diesel away, let alone sell it)