Most of the cops in NYC live in NJ or in cheaper neighborhoods in Brooklyn and Queens. No cop could afford mid town Manhattan. Even though cops and many nurses in NYC make over 100K they couldn't afford Manhattan.
Cops don't live outside of the city because they can't afford to live here. Everyone who is not a uniformed officer that works for the NYPD (administrative, etc) has to live here and they are not all making hundreds of thousands of dollars.
No one ever accused NYC of being reasonably priced, but it is not impossible for "normies" to live here. NYC is not just midtown or even manhattan. There's nothing wrong with living in an outer borough, but even staying within Manhattan, there are plenty of areas with more reasonable housing prices than central midtown.
Yes, things can be very high priced in central midtown, but even here when you go east of 3rd or west of 9th, rents drop drastically. And most new yorkers know that studios and one bedrooms are the worst bang for your buck, 2 and 3 bedrooms are a pretty decent deal if you are splitting with a roommate (which is common in NYC.)
Also, singles who see a future with each other tend to move in together really fast here to save money on rent. Then there is a decent amount of subsidized housing here. Wages are generally higher here than in most of the rest of the country, but there are plenty of moderate incomes living all over manhattan.