Difference between automated and living labor pertaining to surplus value
This question is oddly phrased.

The main marxist thesis about profit is that firms can't profit from technology, but ultimately profit comes from exploitation of human labor, i.e. by extracting surplus value from workers. 

In marxism, profit always comes from "living labor", in the sense that the price of a commodity both reflects the technology used to create it and also the human labor congealed in it. However,  a firm can't "pay less" machines because machines have fixed values while a living human being can be paid less than their value of their labor if the value of their labor exceeds the value the worker needs for subsistence (e.g. sufficient for their bills, calories, leisure etc).