Bhai,
1. labor cost are just 10% of the nuke sub project so the reason we can do or china can do that so cheaply is all falls.
2. all the chinese stuff costs so cheap because of the economy of scale and use of cheaper options but one can't go for the cheaper stuff in the case of nuke subs.
3. Where is the economy of scale in nuclear submarines which is there in jf 17 as u have mentioned it.
4. Even traditional submarines takes 60 months (5 years) to be ready and a nuke submarine needs much more time as the time taken in testing nuclear reactor (after fitting it into nuke subs) + sea trials + weapon testing takes another 3-4 years.
5. Even if you got lottery or china funds everything and also provide technology, spare parts and assistance it will take minimum of 12-14 years to have ur 1st nuke submarine in the pakistani Navy.