Earlier quoted context omitted.
Someone working low-paid hourly wage work can probably make $20K. A few siblings + their parents = 5 people = $100K. Stagger availability schedules so there's always someone home with the kids, and share vehicles. Suburb of top-tier cities? No. Cheapest suburb of a midwestern city? Absolutely. Again, not saying it's reasonable. Just that it's possible.
So you argument essentially is that economic conditions dictate that within a few decade, there will be no restaurants in major cities.
Total household income. It is possible to accept a lower wage job if the rest of the family is making more. A spouse or older child can add to the family budget even if the primary breadwinner is making more.
Grants / subsidized housing of some sort. College students making a few extra dollars while living in the dorms where the major expenses are paid elsewhere.
Back to the older children and summer jobs. Getting a job to do something over the summer and get a bit of spending money of their own.
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Yes, lower paying jobs within higher cost of living areas are going to be having trouble finding people to work there. This has been a thing for many years. Even in the before times, there were constantly places that had "help wanted" signs out and were paying minimum wage. The ones in higher cost areas of the city were more likely to close resulting in more expensive restraints that can be supported by the people who are living the higher cost of living.