Yes, NS should give a lot of money back. And leave Pakistan for good.
'Setting an example' out of him? I think getting a chunk of money back, deporting him, is a far better 'setting an example' rather than letting him rot in prison where he will still manage to eat Biryanis and bide his time for a favorable political change.
I don't know how much can be recovered from Zardari or Sharifs or etc etc but if even $10 billion are recovered that will go a long ways in lining up water canals--an urgent priority for Pakistan-- reforestation, building tourist resorts, improving security agencies, improving basic education system/schools...
PS. And, no, these are white-collar crimes and cannot be compared with rape of anyone. Such crimes happen all over the world and countries have figured out that it's best to get some money back than to imprison such people; latest example being in Saudi Arabia.