Yes. That results in the best distribution of scarce resources. The opposite of efficiency is waste.

In arenas of scale, yes. If you are the low-cost, mass offering, then wringing out unit economics is all that matters to you. Your customers are interchangeable and you can safely assume that there are more price-sensitive ones than there are those who value morals higher.

Morals are God's concern, therefore it's up to God to enforce them. God needs to reach his hand down and decree to the land that thou shalt not abuse your employees. This reverberates throughout the land and causes the powerful to tremble in fear. They all get together in a room and quietly make plans to appease the masses so they don't pray for blood or start a revolution.

Of course, in this case God is the government. Given enough political pressure, legislators can pass laws that change the landscape of commerce. Pressure can compel prosecutors to prosecute, regulators to punish. The threat of these punishments is often enough to keep the unscrupulous in line and allow the virtuous to have their say.