The business proposition is really simple. On the manufacturing end alone, you need at least 20-40k vehicles a year to make a plant cost effective. 20-40k of ONE model. That's from the perspective of the plants that stamp the body panels and build the chassis.

On e research side, you probably (because I have no exact figures for this) need a hundred thousand or so of one model to justify the engineering and development expense. The engines themselves require billions of pesos to simply develop. Given engine development costs can run into the billions of pesos, you're looking at the need to sell well in the hundreds of thousands to break even over several years of the engine's life.