You're putting the cart before the horse on the heated seat argument though. It's cheaper to have one factory line for the seats. Ideally you would pay the same

You're putting the cart before the horse on the heated seat argument though. It's cheaper to have one factory line for the seats. Ideally you would pay the same price for the car without heated seats whether or not the hardware was physically there. It's the same thing they ran into with the software locked batteries. The goal is to have minimal overhead to try to drive costs down on Model 3, and making the SR just a software limited version of SR+ actually ends up pushing the overall cost down, rather than having to set up an entirely different line that does the cloth seats and the aluminum roof.