Bribing elected officials
In the American Revolution, privateers transported arms, munitions and tropical products to the American continent. ... Following the American Revolution, many former privateers became captains on merchant ships, because without war, privateering was no longer needed on such a large scale.
Answer:
The costs of passing a bill that prohibits child labor is precisely that all the labor that children could have provided for the economy is forgone. So in pure economic terms, there is a loss of value, a sunk cost.
However, the benefit is both economic, and social. The economic benefit is that children will instead go to school, and educate themselves to become more productive workers in the future. And the social benefit is a fairer society, and wealthier too.