How do I do it (pay my rent)? Well, I have a job...
Seriously though, New York is hardly the most expensive city in America--cost of living in DC, SF, LA, and Boston are as high, if not higher. As others have said, not having a car certainly helps a lot, and the outer boroughs are great for those who can't afford/don't want to pay Manhattan rent.
"You travel alone because other people are only there to remind you how much that hook hurts that we all bit down on. Wait for that one day we can bite free and get back out there in space where we belong, sail back over water, over skies, into space, the hook finally out of our mouths and we wander back out there in space spawning to other planets never to return hurrah to earth and we'll look back and can't even see these lives here anymore. Only the taste of blood to remind us we ever existed. The earth is small. We're gone. We're dead. We're safe."
-John Guare, Landscape of the Body