The value of a human life varies enormously on perspective and how people judge this so-called 'value'. Is it how much money they earn, or is it how much they mean to their families and friends? Is it how many of their kind there is, how easily they can be replaced, or is it their hopes and dreams and individuality? And can a person be paid for?
The view of business people, such as mnine owners and those that sell the phones which use Coltan, is most often only about financial interest. "A child in the Congo -- why, there are hundreds of them, and their death would not cause any dip in the economy. Why should they be spared? No, they are of use to us. We will not pay them more, for they do our work anyway." In this way, they are effectively saying that the children are worthless. And yet their mothers would argue the opposite.
There are, in the past, examples of children in developed countries being thought of as worthless. For example, in Victorian Britain they were regularly used as chimney sweeps, which was dangerous and sometimes fatal. Going even further back, during the time of Leonardo da Vinci, there was a woman -- I think her name was Lucrezia Borgia -- who, when her children were threatened to make her submit, lifted her skirts and said, "Do your worst! I have the means to make more!" In these circumstances, she too was implying that they had no sentimental value, but that may have been just a 'show'.
In complete contrast, there is the Christian belief that people are unique and priceless, which is why Jesus was willing to die for their sake. They think that every human being was made in God's image. Furthermore, they believe that however rich or poor they are, they are still equal. This is one of the reasons why the abolitionist, William Wilberforce, spoke out so much against slavery: he was a strong Christian and his faith drove him to tell people that rights should be equal.
But there is always an opposite. For example, people trafficking and slavery exists today, even in the UK when it was supposed to be abolished over two hundred years ago, in 1805 (2005 was the 200th anniversary, and yet there are more slaves alive today than there were during the entire British slave trade). In a book by Steve Chalke, 'Stop the Traffik - people shouldn't be bought and sold', there is a story of a girl who was trafficked for sex within the UK itself. It was a true story, and one of the most powerful things she said was, "They made me feel that all I was worth was what someone would pay for me." This is the view of the traffickers, who see young girls as objects to be exploited.