This is my second attempt, so ive cut the content a little.
: If life has a price, then it can be exchanged for, say, an amount of money. Therefore, if I steal amount X from you, according to you, my life should be forfeit. I think we can all see the nasty implications of that line of reasoning.
Life has the price (value) that you set for it. Only you can determine the value you derive from being alive. Another person cannot. A person who says "but youre only worth $50 to me" does not usurp your self value any more than a person saying "but the mkt value of this house is only $100k" can usurp your choice not to sell it at that price.