I understand the theory behind the production-line savings, but 100% do not believe that those savings will be passed on to the consumer, and am unconvinced that it actually is more cost-effective/materially efficient (incentive-wise, it’s in the best interests of the car manufacturers to convince us that this will be a good thing for us in the long-term).
They’re manufacturing the various components (like seats) on totally separate lines from the car and then assembling them. If every single component manufactured is the fanciest, priciest version—if every seat has a heater, a fan, and internet connectivity so it can be activated or locked—that’s certainly going to result in a more expensive base vehicle price vs manufacturing lower-tier components and feeding them into the assembly line as necessary.
A great example would be the Tesla batteries. They’re absolutely not putting the same battery in each car and then locking the ability to charge it beyond a certain point. Materials costs are a huge factor.
A non-vehicular example would be phones. There’s a reason why every iPhone doesn’t have the same components that are just subscription-locked.
The FSD side of things does feel different, though, I agree with you there. You’re paying for a consistently-updated, software-based service, but that’s not at all comparable to having to pay the original manufacturer to activate, say, the blind-spot indicators on a used car (unless they’re coming out and upgrading your mirrors from time to time).