Two words : Slave Labour.If you had to separate the average human into its components, the most valuable part will probably be the 1Kg heap of iron. All together a human is not worth much more than R200-R300 at current resource prices. A baby will obviously be worth a bit less. Give or take.
The little people can get into nooks and crannies bigger kids can't. Also, rather train them young.Its probably cheaper and easier to buy 'ready to work' slaves than nurture one for 10 years till its fit for hard labour, unless you need someone to build sand castles all day??