Reducing commute and other wasted time is probably still the low hanging fruit for most people. If your work is sufficiently varied, I don't see how 60-80h/wk is unsustainable at at least 1.5x the work you'd accomplish in 40h, if (and only if) the other hassles of life are taken care of for you -- no cleaning, commute time, etc. I don't think I could do a single task for 80h/wk productively, but I could certainly do…
But should you? Your employer will not reward you for it with anything that could be considered reasonable when compared to the value you are creating for them. What people can do, and what employers are willing to pay for, are two very different things. Employers, by and large, have adopted a strategy of paying employees as little as possible, divorcing their compensation from the value of their work. Capitalism say…
The lack of correlation is primarily due to inability to measure contributions vs. an effort by employers to selectively screw high achieving employees. If you had perfect visibility into the current and future contributions of employees, it actually would make sense to pay the 10x employee 10x more than the 1x employee (and arguably being able to make a team of 5 x 10x employees would be worth way more than the equivalent salaries of 50 regular employees, since a 50 person team would be so large as to have 2-3 layers of management, much higher support costs, etc., so just paying the smaller team 10x as much would be a bargain.)
For a variety of reasons this isn't really done directly with cash compensation (taxes, measurement, supply shortage, envy of other employees, politics with managers, etc.), but rather by the 10x teams being startups which may get purchased.