Bryan Caplan theorizes:

 With 0 fixed costs, wages fall to MC=0, but total output – and GDP per human – skyrockets.  Human owners of land, capital, and other non-labor assets capture 100% of all output.  Humans who only have labor to sell, however, will starve without charity or tax-funded redistribution.

In other words, if a robot can provide labor at a very low cost, all human labor would become obsolete. Those who can earn an income from non-labor taks, such as owning property, investments, etc. would profit immensely. Those who can only provide labor would have no meaningful role left in society, and would be forced onto the public fisc.

This is something I have thought about for some time. I am much less worried about a robotic apocalypse, like in Terminator or the Matrix, than a society where human productivity becomes obsolete. Will there be a Marxist revolution against the robotic-bourgeoise?