There is no scientific reasoning behind [...] putting a monetary value on a human life. Sometimes what Dawkins calls reason is just a mask for his prejudice.
You are confusing science and reason.
Science has no need to put monetary value on anything unless money is a parameter in a particular experiment.
Reason says that you must put a monetary value on human life when spending money that can affect human life. The UK Health Service, for example, uses a figure of around $40K per year of human life in order to decide on the cost-effectiveness of various medical treatements, valuing an adult life at about $2-3M. Aid agencies will have a pretty good idea of how much it costs to save a life in various parts of the developing world because they have to deploy their limited resources in the way that saves the most lives.
In these situations refusing to put a monetary value on a human life is just illogical sentimentality.