Cost of punishment versus cost of prevention?

Well.  As you can see.  Blank.  I have no answer.

But my previous post on rising vigilantism in Malaysia has really got me thinking.  Logic tells us, surely the cost of prevention is a lot lower than the cost of punishment (total cost incurred related to crime).  But I really want to put a figure to it.  Because nothing convinces us better and harder than seeing black and white numbers straight up in our face.  Nothing helps us crystallize solutions better than hard facts.

So, I'll need any help that I can get.  If you could just kindly point me to available resources (Malaysia or best practices on international shores), that would be deeply appreciated.

Who commits the crime, where, when, how and most importantly why?  It's so easy for us to generalize criminals as 'immigrants' but yea this is public perception but does it help the solution if we're so polarized?  So who else?  Poor people?  School drop-outs?  Who?  If we could intervene when they are 5, we not only spend less public funds on punishment but we're able to prevent hundreds and thousands of crime unfolding a decade later.  But before we decide the point of intervention, we need to know, exactly 'the point of intervention'.  What if they are not Malaysians?  

Much much much appreciated.  Thanks in advance :)