And you're STILL assuming that the 75-hour work week you would not get a severe case of burnout and turn into a 0-hour work week you for a year, after which going back to the regular schedule would simply not feel like an option.
Even if you didn't assume that, there is still an underlying assumption that working harder and getting more more money will in the long run make you happier than working shorter hours and having less.
I guess it depends on how much you are making. For 300k, I'll work 75 hours a week and not burn out. The incentive is there.
If you con me into working 75 hours a week for 70k, I'll burn out when I realize I've been wasting my time propping up a loser.
I'd imagine most people are the same. Pay them enough, and they will cope with terrible conditions. Con them, and they will lose interest a lot faster.
You can still burn out at 300k. Actually, you might be more likely to burn out with a higher salary, because you will find it easier to rationalize abusing yourself by cutting sleep, healthy food, friends, etc.
Burnout is an unconscious phenomena - you don't realize you're burning out while you're doing it, and in fact it often feels quite exhilarating. It's pretty easy to be making 300k and suddenly find you just can't perform the job duties that net you that 300k. It's not a matter of choice, determination, or coping, it's a matter of your brain refusing to do the things it needs to do.
Even if you didn't assume that, there is still an underlying assumption that working harder and getting more more money will in the long run make you happier than working shorter hours and having less.