Re: Folks, downvoting...
I didn't downvote you, but I think there is quite a bit of confusion here. I'm not sure I understand what point you're trying to make, and some interpretations of your posts can be taken as going against the grain here.
At first, I thought you were implying that you were self-employed. In that scenario, your main cost is your time, therefore the distinction between output per unit of cost and output per unit of time is not really relevant. The point, then, is that output per hour will fall sharply as the number of hours per week increases. If this is not true for you, fine, but you're an extreme outlier, and a lot of that is probably due to factors that cannot be generalized (i.e. not everybody can work in software). Because of that, you can't use your example as proof that long weeks are a good way to organize work at a societal level. Also, in any case, a self-employed person can simply be okay with the productivity loss, because it's still worth for them; I myself work very long weeks some times.
From the last couple of posts, though, it looks like you are talking about an employer/employee situation. This is drastically different, because the cost to the employee is their time, but the cost to the employer is the employee's wage. Which means that the definition of productivity can look quite different depending on which point of view we're taking, hence the confusion.
Most of the discussion here revolves around the fact that nearly everyone knows and accepts that output-per-hour falls as hours-per-week increase, and therefore when the Infosys CEO calls for people to voluntarily work long weeks to "increase productivity", the implication is that he's essentially calling for raising employer-productivity (get more work for the same wage) by hurting employee-productivity (work more hours for the same wage or only marginally more). The main thing that everyone here is opposing is the idea that this can be truthfully called "increasing productivity" for society, as the Infosys CEO is trying to claim. It is not; it's merely a net transfer of value from employee to employer. Worse, it's an inefficient transfer, which means that it's a net loss for society.
In the last post, you seem to be appealing to the notion of competition to claim that this situation is necessary, that companies where staff doesn't work 70 hours will be outcompeted. This is problematic at several levels. First of all, even if it was necessary, it still would not be good; attempting to present this phenomenon as ethical is likely to attract downvotes. Secondly, but most importantly, it is not necessary at all. Nations can and do enact legislation to prevent extreme employee squeezing, in fact most Western nations do, and have done so for a long time, and they are some of the richest nations in the world. Arguably, not in spite of this, but because of this: because, as I mention above, increased productivity by squeezing is not increased productivity for the nation; it's a productivity loss for the nation; it's just increased productivity for the employers. A free market that allows this is bugged and needs fixing. It doesn't need calling the bug a feature.
Denying this is not "an inconvenient truth"; it's just a different opinion - which, however, really ought to confront the fact that nations with high labor standards are really rather successful, good places for people to live, compared to places like India. Obviously, it's not just that, not by far, but you can't not face this, appear to tell everyone they're deluded if they don't agree, and then be surprised at downvotes.
I'd also note that, as a freelance, I've worked with a sizeable number of companies, and, anecdotally, the ones that routinely squeeze employees the most are usually the ones that have very serious process problems, which they are masking by squeezing employees - for example, having crunches that could be totally avoided by being better organized, or big dead weight somewhere. That situation is unsustainable long-term, not because you can't squeeze employees forever; sadly, you can, just get more employees when yours break. But because it's brittle. As soon as something unexpected happens, you're dead, because you're already squeezing and you can't fix process in a month (well, you can always cry for government subsidies, because it's true that everyone is a socialist with other people's money, but it's also true that everyone is a capitalist with other people's money). Around here, a lot of firms that worked like that were wiped out by COVID, for example.
The ones where people usually work more or less what their contract say, they are the ones I'd deem most likely to survive long term, because their process works. If something horrible happens, they can squeeze employees for a while. That can be done easily and immediately. But if you rely on it, you have a problem. I would call that the real "inconvenient truth".