For the same reason. Vehicle seat are, for better or for worse, typically model-specific. Before there was Tesla there was nobody making Tesla seats. Would anybody be surprised if they start outsourcing that soon, given that they now have enough volume to attract third party suppliers and seat manufacturing is certainly not their competitive edge?
> A lot of companies just outsource that and lose out on the profits, it is one of the reasons tesla has such high margins.
Vertical integration increasing margins is just an accounting trick.
It costs $5 to make a widget, the widget maker sells it to the car maker for $6, the car maker sells it to the customer for $8. The non-vertical car company has a $2 unit margin, the vertical car company has a $3 unit margin. But to get it they take on all the risks and expenses of the widget maker.
If making widgets is a commodity market then the $1/unit is going entirely to fixed overhead (otherwise someone would charge less and gain market share). Taking on the fixed overhead in exchange for the $1 is breakeven and increases systemic risk by reducing supply diversification. But on paper your margins increase by $1.
