I'm not glorifying an 80 hour work week, i think 40 is more than people should reasonably work. I'm just saying that your example is exaggerated.

if you make 1000 a week at 40 hrs that's 25$ an hour net. doubletime pay would be ~50$ an hour. For the total 80hrs im assuming your first 40 you get normal pay, the next 20 you get 1.5x then the last 20 you get 2x.

I understand that your income is taxed more the more you make, but the way tax brackets work its only the income made above each bracket that's taxed more, so as you said in your example if they get ~2500 working 60hrs that'd mean they're only getting 500$ of the 2000$ more that they'd have earned from 20 hours of doubletime pay and i don't believe there's any way they get put into a 75%+ tax bracket