Most true suburbs aren't within the big city limits, so I'm not sure your point is well-founded. For example, in the DC area, the suburbs aren't even in the same state as the city and yet the suburbs seem to be thriving.
The road network expansions and maintenance required to support the suburbs does. Ottawa has this exact problem. They are widening inner-suburb roads to satisfy demand created by outer-suburb development. A double-whammy.
Those suburbs outside the city limits still need money. They get it from state and federal funds which were mostly collected from people in the city limits. For example the Highway Trust Fund as one of many examples. If you check the per capita spending, it's higher for suburbanites than urbanites but the urbanites are putting in more money.
Absolutely not in the case of the DC metro area, on both the MD and VA sides. Those counties subsidize DC proper in various ways, along with the less populated portions of their own states, and because the median household income is so high, they also pay a disproportionate amount of federal income taxes when compared to DC residents.
I also have no idea why you think city dwellers are the primary contributors per capita to the Highway Trust Fund which is funded via a tax on fuel (i.e. miles driven).
The tax on fuel has not been able to keep up with expenditures for the Highway Trust Fund for two decades; now a third of the money comes from the General Fund.
they aren't putting as much in as the city by call kinds of measures. It generally cost up to 4-5x to maintain suburban areas vs urban. High income suburbanites don't make up that difference. They're subsubdized by the urban citizens.
The suburbanites pay for that maintenance, and there are many other costs to city living that urbanites like to ignore (significantly higher expenses on emergency and social services for example). It's not nearly as straightforward as urbanites like to claim.
One thing that is absolutely clear is that commercial districts subsidize residents in every jurisdiction, and urban commercial districts rely on commuters (from surrounding suburbs) to thrive.
There’s been somewhat of a continuous cycle of movement with the upper class of America that goes something like this:
1. Move in to the latest newly constructed suburb with low taxes and fresh housing stock
2. Infrastructure ages, tax rates increase, housing standards evolve, the upper class moves to the next new suburb built on former farm land
3. The inner suburb declines, becomes low-income, companies leave, and infrastructure crumbles. Municipal debt piles up, sometimes the city goes bankrupt.
This is especially obvious in cities where regional growth didn’t continue upward forever.
I recommend reading up on Strong Towns’ growth ponzi scheme content.