So, labor is not like milk because milk is produced by cows, but labor is like a loaf of bread because they are both produced by human beings?
Nope. Human beings produce labor. That's literally ALL a human being produces. Not loafs of bread; not cars; not battleships; not computers; not even software.
Labor, in turn, produces products of varying quality and value, depending on the person performing that labor, the skills they possess, their work ethic, talent, training and resources. Certain types of labor are more valuable than others, depending on the person who produces it (the labor of a software engineer is a lot more valuable than the labor of a burger flipper, for example). Labor can be bought and sold in various ways on the market, and can be traded between companies, upgraded, invested in, eliminated or replaced.
Human beings can't. Human beings have intrinsic value as
people. We produce labor to survive because survival is our imperative as living beings and our right as members of a free society. The fruits of our labor -- bread, cars, battleships, computers, software -- are bought and sold and traded by companies, retailers and ultimately by other people who also produce labor to be able to purchase those products for their enjoyment.
Human beings, however, have no market value. We cannot be bought and sold, we cannot be liquidated for cash commoditized as assets. Neither does human survival have a quantifiable value, nor human happiness, comfort, health or safety. These are things that exist OUTSIDE of economic considerations and have intrinsic value in and of themselves. The cost to achieve (some of) those things can be calculated on a case-by-case basis, but none of those have an inherent monetary value.
It's really simple, actually. The work done by a person has a price; the person who does the work is priceless.