The city of refuge must also be safe. Ropes can not be used to cord off areas and knives may not be sold within the city. This is so that the relatives of the victim do not come to the city for easy revenge. It is absolutely forbidden for the murderer to pay ransom to the avengers so that he can be set free from the refugees life. Ransom would mean that a human life has a dollar value.
Human life is priceless and ransom is repulsive to a Torah way of life.
The person who murdered by mistake can move back home only after the High Priest dies. This in itself is a discussion. Archeological research has found that in the ancient East the pagans had cities of refuge. It is very beneficial for us to compare pagan justice to our holy Torah. This should strengthen our belief in the Torah.