Then it seems to be more of a problem with excessive regulation then suburbs themselves.
As a thought experiment, even the wealthiest city in the world couldn't afford a single bridge if regulations required bridges to be made out of stainless steel.
- Environmental regulations requiring NEPA analysis or categorical exclusion
- State laws on who can perform road construction
- Construction codes for roadways and bridges
- Miscellaneous overhead for other areas (e.g., Human Resources, accounting, etc)