It's important to include all the downstream affects of technology-driven disruption when considering where it might take us.

For example, a post human labor society not only has a drastically reduced per capita income, it also is deflationary. The salaries no longer paid to humans can either go in the pockets of passive investors, or used to reduce the cost to consumers of goods and services. Competition and reduced demand will ensure the latter.

That being the case, the amount of UBI needed to support basic needs should be low enough to make it function reasonably well.

Taken to an extreme, if everything costs nothing, there's no need for income to buy anything. Absurd, I grant you. But it's where things are heading.