In an idealistic capitalist society, everything has a value, and everyone both knows and agrees on what that value is.

What we have is some bastardization of this where anything you don't see or can pay others to not see gets swept under the rug. Environmental damage? Not my problem.

Human exploitation and slavery? It's not my country, so who cares?

The actual cost of human exploitation is paid by the country that the diamonds come from. The change to social structures that continue to systematically oppress in the interest of power and profit, the wanton destruction of natural resources and the environment poisoning the land for future generations, and the dependency it creates in the economy.

Lab grown diamonds don't have these issues, and that's an uncounted part of the savings.