(Opps. Wrong category, sorry.)
First crack at a self sufficient factory:
Mid-range Sedan $30,000 (10% profit margin)
Driver side air bag
The two features were to give those slots something to be supplied with. All sub-components made in-house. All slots used, but only efficiency upgrades, except for AC and air bag.
(Cliff: The Fit Arcon slot calls for units, even when AC is not being installed. Bug or game feature? Your call.)
30ish cars in showroom, and they are selling. I can do better. This is first stable production.