> (when the max their productivity is worth relative to AI falls below a living wage), humans will continue working side by side with AGI as even relatively unproductive workers

This assumes that humans will be unwilling to work if their wage is below living. It depends on the social programs of the government, but if there is none, or only very bad ones, people will probably be more desperate and thus be more willing to work in even the cheapest jobs.

So in this overabundance of human labor world, the cost of human labor might be much closer to zero than living wage. It all depends on how desperate to find work government policy will make humans.