Why do people think it's easy to make perfect cars in small numbers? I would assume that defects will go down as they scale up, as things will become less manu

Why do people think it's easy to make perfect cars in small numbers? I would assume that defects will go down as they scale up, as things will become less manual and more automated, and they find the common problems and fix them at manufacturing time. Are there other car companies that started from nothing that went a different direction? Did they start with nearly perfect cars then get progressively worse as they scaled up? Did they plan to mass manufacturer cars?