I don't know about overall manufacturing cost but clearly when OEM have a zillion different engines to make (and even engines with similar capacity could be physically different) and regularly update, electric motors would be much easier plus could pretty much be one size fits all (with electronics and software differentiating the models or limiting output for entry bikes).The bike is a fundamentally cheaper machine than a combustion bike - fewer parts overall and the expensive parts (batteries) are plummeting in price thanks to the huge volumes being made for EVs.
The big challenge for Stark is their relatively low volumes but those are rising.
I expect that Stark can make a profit at prices that combustion bikes will find it hard to match.
I guess battery assembly is more costly and time-consuming, even though it's already automatic at Stark. They could possibly carry designs between different models, 3-4 battery sizes should be enough for a whole range of bikes.
Would love to know a bit more on the economy and manufacturing cost of EV vs ICE, there must be some info related to cars out there.