But the streamlined manufacturing is still more expensive than no heated seats. So someone needs to pay for it. There are two reasonable options 1. charge everyone a bit more by including it as a standard feature 2. charge only some people significantly more so that only the people who find heated seats worth it pay the cost.

It isn't double dipping, in no scenario does it make sense to physically make two models, it is more expensive for no gain. The question is just how you charge people for it.

(Now subscription seems like an awful model, but a paid upgrade for some people makes sense to me)