The battery pack and associated circuitry is a array of solid state components.
An internal combustion engine has thousands of different parts - many of them moving, unmonitored and uncontrolled.
The EV is much simpler to manufacture and maintain. The GM EV1 was famously robust and low maintenance. Personally i believe this is one of the reasons the previous generation of EV's were canceled - it radically changes the profit spread on a vehicle. The old school manufacturers make a lot af profit on vehicle maintenance and parts - this is about to change.
The part count on a typical automobile is 30000 according to toyota - I would love to know what the Model S count is - even with the 6000 battery cells.