How best to leverage that resource? I believe that kidnap and ransom is one traditional answer.

It would be difficult to nail down a value in general since it will vary from person to person.

But to a capitalist market a mother's love of her child is of huge value. Because that child is immediately a part of that market due to the money the mother spends to raise the child. Then the child eventually grows up to enter the market as a consumer to spend money on herself or maybe enter as a producer. Eventually she may have a child of her own to repeat the cycle. Without children a capitalist market eventually dies and a mother's love is one way to help its survival.

I'm on your side, but I think this is a bad example or poorly stated. Mothers feel all kinds of pressure (from many angles) to, for example, buy their kids the latest toys or coolest clothes as an expression of their love. Etc.