How do most young people afford NYC?

This is my 2nd time visiting NYC.

Lots of people take student loans for their undergraduate or graduate education in their early 20's.

In my view, from experience in NYC. people spend money liberally.

Meals, rents, cabs, tips, etc...

For people who are paying back debt, how do people afford NYC? Do people work side-jobs to help pay for expenses? It seems unfathomable how people spend so liberally when things are so expensive in NYC. How are people's savings rates? Are there special tricks to help save money in the city?