Psychologically, I don't think the value of children has changed. Mourning the death of children is as ancient a literary trope as any.

But from a microeconomic point of view, children were more valuable in pre-industrial times. Most people worked in agriculture or the trades and lived in multi-generation households, and children were necessary to help with chores and eventually take over the main occupation and care for the elder parents. There was no retirement fund, just your children. Food and clothing were more expensive and childbirth was risky, so children represented a major investment. That they were sacrificed is a testament to how much value people placed on the ritual, not the lack of value of children. See also how valuable farm animals were sacrificed.