The moral justification for the existence of poverty is one of purpose and worth through contribution to society. The family member of an ultrarich baron can sleep at night mostly due to the idea that those who are rich contribute value to humanity as a whole, ergo those who are poor simply aren't working hard enough or contributing in a meaningful way ("just world fallacy" etc)

When AGI becomes reality, that reasoning disappears. When everyone's worthless, no one is. Thus the scenario you speculate about would need everyone in the upper echelons of society to be consciously, openly sadistic power-hungry people, which is not the case even when taking into account the higher dark triad rates among them.