At least the Incas placed a value on the lives (because they thought the gods would be pleased.

Pre-Columbian people were rather war-like. They committed heinous acts against each other. So adding child sacrifice on top of it takes the cake. The Aztecs were also vicious and sacrificed thousands. I do understand that there are limitations in using the lenses of the present to understand our past history. It's difficult to get in the mind of someone who lived so long ago in such a strange place to discern their motivations and the evolutionary advantage they gained from it.