From another point of view...
From another point of view, in an ideal society, which Islam attempts to create, most of the economic activity is carried out by men. When we look at the general economic responsibilities of men we find that men have duties that women have been excused from.
While the most important responsibility of a woman, but not the only one, is to manage the cornerstone of society, in other words the family, the most important duty of man, but not the only one, is to provide for the economic needs of the family. Aside from this, the daily expenses of the children are upon the shoulders of the man not the woman. Therefore with his departure some people who should be looked after find themselves at a loss. This vacuum must be filled by some means.
It is only natural then that the blood money of a man should be more than that of a woman. This matter has no relation to the essence of men and women. Rather it relates to the external accidents that are incurred by a family. When we take into consideration all that has been just said, we can come the conclusion that blood money is not a means by which we value men and women. Their difference in this matter is not something to be objected to.
From another point of view the economic responsibilities of a man necessitate that in some matters (like blood money) that are directly related to economics a certain difference between men and women show up. There is no difficulty in this matter. Men are stronger than women and are capable of performing more difficult tasks than women. Their existence provides peace and tranquillity to the family. From another point of view, with their loss some people are left without a helper and provider.
It is therefore natural that their blood money be more than that of women. We conclude this answer by turning our attention to a point that is not without subtlety and by answering two questions. First of all, man’s blood money is double that of woman’s in the case that the blood money should reach one third of the required portion. In any other case, their blood money is equal. If her blood money’s being half were a proof of her inferiority to that of man, then in all cases it should be half.
Secondly, just as men have more blood money than women, they are also responsible to participate in the money paid to the family of someone killed or injured by one of their family members. This is while women are excused from such an obligation.