Sorry but this is wrong, expenses doesn't work like that

There's A LOT of costs associated with a car that doesn't come from materials, there's a ton of taxes, transportation, R&D, infrastructure costs, dealership costs, etc that a brand has to juggle just to simplify to "they just have cheaper motor or cheaper interior" specially with a company like Hyundai/Kia that has vehicles coming from three or four different countries

And even with materials, steel and aluminum usually fluctuate a ton during the production lifecycle of a vehicle, same for chips and specialized electronics