Maybe for some cities... but definitely not for the every case. There are are multiple small towns around me which are very suburban and have low density house

Maybe for some cities... but definitely not for the every case. There are are multiple small towns around me which are very suburban and have low density houses. They are independent, so they have their own budget -- and they to keep it pretty balanced, at least judging by their road condition. They get a tiny amount from federal/state level (less than 1% of their income). And you cannot say "it is all subsidized by high-density areas", because those towns do not have such areas. As far as "taxes to the local city" -- the city their residens are likely commuting to gets plenty of money from the all the commercial housing taxes (in 2020, it got 65% of the taxes from the commercial properties) Seems pretty sustainable to me. Yep, it is expensive and I (for example) cannot afford to live there, but they have no problems selling houses. And they have great parks, too, so I like that they are around.