Cars that look and cost nothing alike frequently share their fundamental structure. The reason is that designing that structure is where most of the engineering money goes.
The platform is the expensive part
A vehicle platform defines the floor structure, the suspension mounting points, the crash load paths and the basic packaging of powertrain and occupants.
Developing one requires years of engineering, extensive crash testing and dedicated manufacturing tooling, all of which must be paid for before a single vehicle is sold.
Spreading that cost across several models rather than one is the difference between a viable programme and an unaffordable one.
Modern platforms are adjustable
Older platforms were largely fixed in size, so sharing meant building similar vehicles. Contemporary ones are designed with deliberate flexibility.
Certain dimensions are held constant, typically the distance from the pedals to the front axle, while wheelbase, track width and rear overhang can vary.
That allows a small hatchback and a large crossover to be built from the same architecture, using the same mounting standards for shared components.
What differs sits above the structure
Body panels, interior design, sound insulation, suspension tuning and equipment levels are all comparatively cheap to change and are where models are distinguished.
Suspension tuning in particular does much of the work. The same hardware calibrated differently produces vehicles that feel meaningfully unlike each other to drive.
Buyers therefore experience real differences between related models even though the parts responsible for those differences are a small fraction of the total.
Sharing extends across brands
Within a group that owns several brands, platform sharing crosses brand lines, which is why a premium model and a mainstream one may sit on common foundations.
The premium version usually receives more sound deadening, different materials, additional structural reinforcement and more expensive suspension components.
Managing this without eroding the premium brand's distinctiveness is a permanent tension inside large automotive groups, and it is not always resolved successfully.
Shared parts concentrate risk
When a component is used across many models, a defect in it affects all of them, which is why some recalls span several brands at once.
The same concentration applies to supply. A shortage of one shared component can halt production of vehicles that appear to have nothing in common.
Manufacturers accept that exposure because the alternative, engineering unique parts for every model, would cost more than the disruptions do.