> his starting point is that labor is identified with value
This is a large mistake. For example, spending an hour on an exercise bike is certainly a lot of labor input, but nothing of value, since nobody will pay you to cycle on an exercise bike.
You're making a large mistake too. For example, that nobody will pay you to cycle on an exercise bike does not mean your labor has no value -- after all, if you're in better health, you will be more productive in the hours you're not on that bike.
(to make my point more explicit: in Marx' definition of labor he implies labor of enterprise, not just spending calories. Just like your definition of value implies financial value, not just any positive outcome. I'm purposefully misrepresenting your definition of value just like you're purposefully misrepresenting Marx' definition of labor.)
> Just like your definition of value implies financial value
When the discussion is about economics, that's what matters. There is no intrinsic value to labor.
> Marx' definition of labor he implies labor of enterprise
The economic value of labor has no necessary relationship at all to the effort or time supplied by the laborer. If Bob works inefficiently, his labor is worth less than Bill who works efficiently, even if they both work exactly the same length and effort.
This is a large mistake. For example, spending an hour on an exercise bike is certainly a lot of labor input, but nothing of value, since nobody will pay you to cycle on an exercise bike.