Here's what I don't get: India has about one hundred nuclear weapons. Yet they can't invest in a sensible sanitation infrastructure?

I know at some level this is nonsensical. The question really is more about whether this is a problem of priorities rather than capability or finances.

The average income in India is reported at somewhere around USD $100 per month. How many people and resources do you need to construct the required infrastructure? How much would it cost?

I don't know the cost of a typical nuclear weapon and the required support infrastructure. It can't be cheap. A billion dollars would put a million people to work for ten months. Is it a matter of misplaced priorities?