Not really the same thing, but Tesla does it on a 10x scale: The monthly cost of the FSD Subscription is $200/mo, costing $14400 if you were to pay for it over the entire 72 month loan, but you can also choose to buy it outright for $15k ( $16800 over the loan term at a 2% interest rate; at current interest rates of 7%, $21300) - and for FSD, you can cancel anytime to save money if you don't want it. With the loan, you can't get a rebate for removing the feature.

Of course, for things like heated seats, the question is whether or not they've actually reduced the price of the car to account for the additional post-sale revenue. For Tesla, the Model 3 started out at $35k so heated seats being an additional charge at first made a lot of sense, but as it crept well over $40k for the standard range/RWD version, it started to look like a money grab and IIRC it was the 2022 refresh that removed the heated seat post-purchase requirement on the RWD trim.

Meanwhile many of the "lower end" brands started to include stuff into standard that you had to pay extra in higher end brands - because they are actually competing with their competitors on best deal

Is it possible that consolidating options so that there's fewer hardware variations of a car (with heated seats or whatever being a dogteare toggle) makes manufacturing more efficient?

BWM sells heating seats subscription for $18/mo.

"Heated seats" is just a piece of wire put into seat, some $1 (probably less) micro to turn it off and on and some $0.1 sensor.

I wouldn't be surprised if even few % of buyers buying that would cover for having to fit extra (and not have separate SKU for heater-less seats)

I installed myself heated seats in my car. Installation set, heating pads, switches, wires and relays for two front seats was $56. I would say it costs manufacturer $10/seat.

JOOI, can you arrange to only pay when it's cold enough to need them, or is cancelling/resubscribing the huge pain one might expect from such a scheme?

You already know that answer to that, because making cancelling annoying will make them more money.