Because it's illegal to pay so little, and nobody would do it for that price anyway, except for maybe your own children, who do it for that price plus the negative incidence of an asswhooping. If it were affordable for common people to have servants or slaves, they totally would. Machinery priced slaves out of existence. The next frontier is for value-added centralized industrial manufacturing to be priced out by distributed manufacturing and recycling, not a return to the days of domestic servitude.
He mentions mentally disabled people specifically, who have lower minimum wage levels in some jurisdictions.
I was lucky and someone was interested in the old one to try to fix it, or to swap parts and make their current one look nicer, so I didn't have to haul the other one away to the dump, but that's something the installer will typically do.