You example, again, is only valid for San Francisco.Maybe try doing it and see for yourself? It's not as simple as you think it is. $80,000 after taking out a modest 10% for 401K brings you down to $72,000 a year. After taxes, that's about $54,000 a year. $54,000 a year is a monthly income of $4500. So now that we've established $4500 a month is what we have to work with, let's see how quickly that can go.
Rent here will cost you about $2600 for a single bedroom. Right off the bat, we're now down to $1900. Average student loan is about $400 a month. Now we're down to $1500. In the Bay Area because public transit isn't so great, you might need a car. Take out another at least $500 for a car payment, car insurance, gas, and car maintenance. That could easily be $600 too, but let's calculate at $500. We're now down to $1000. Groceries and other food expenses for the month? $100 a week, or $400 a month, and we're now down to $600. Add in utilities and Internet at about another $200, and we're now down to $400 a month. Entertainment budget such as things like Netflix, maybe a book, etc under normal times and not during the pandemic, let's say $50, and we're now down to $350 a month. See how fast this is dropping and we haven't even gotten to daily household expenses, clothing, etc.
Now can you scrimp here and there to adjust some of that, sure, but I wouldn't say someone was poorly managing their budget by not doing so. The cost of living is higher here so you pay more for not just things like rent, but also food, gas, utilities, etc. I won't say that they can't get by on $80k, but I won't say someone who is living paycheck to paycheck here on $80k is managing their budget poorly either.
That is one city in the entirety of the US. If you are paying $2600 for a one bedroom on $80,000 you are living above your means anywhere else in the US.