Your use of political boundaries is confusing the issue and masking what's really going on. The middle class supports the poor. (Technically the rich do too, but there's not many of them to make the bulk of contributions and also the burden they experience by their support is so dramatically smaller than the middle class as to be practically negligible, and they have many, many ways to avoid contributing and holding onto most of their money)

The political entity of Philly makes tons of money in its boundaries, but all that money goes to the people working in Philly. But those people making tons of money in Philly largely don't live there. They live in the surrounding area and commute to Philly to work. That means the city residents themselves are largely poor and need assistance. But by taking the jobs of cleaning, construction, services and so on, they're supporting the people who are making the money that's supporting both them and the parts of the state out in the mountains, outside the metropolitan area. So the Philly metro area sustains both itself and the outside parts that don't contribute in return.

Contrast this with San Antonio, where it's a very large city, takes up almost all of Bexar county, but once you go outside, it's mainly desert and a few scattered towns, mostly along interstates. They don't really have a metropolitan area. That's a city where a lot of the people making money live in the city itself, along with the poorer residents. So in that case the city is kind of a self-sustaining bubble.

A city like New York is a mix of both, with many middle-class people living in the city along with the poor people, but also a huge commuter population as well. New York is just huge, though, so it in a lot of ways plays by its own rules and has unique challenges.

Now let's look at a place like Potter County, PA. There's not a lot of business there. Or people. Or agriculture. No industry, few roads. Few reasons to travel through there and practically no reason to do business there or to stay. There's not really a way to make a living. As a result they're dependent on outside funding, but they also don't make a significant contribution back to the urban areas. They could drop off the face of the earth, the the people working in the cities would only notice that their taxes would go down slightly. In effect, the amount of money being taken out of Potter country to support Philly residents is practically zero. And when you factor in the money being taken out of the Philly metro to support Potter county, the amount is very deep in the negative.

Not a myth in WA state where I moved from. The Seattle area generates more state revenue than it receives, and the rural areas in the state, most everything east of the Cascade mountains, get more from the state than they pay out. Which is why the western half of the state always laughs when eastern WA talks about forming its own state.