> They have a similar (but smaller) advantage in phones, though that is also due to a very large die size as they can afford to spend more per product.

Can Apple afford to spend more per product? There are plenty of other phones in the same price-bracket as the iPhone, and some like the Galaxy S-series phones surely have the volume, to justify a $10–20 increase in SoC cost to get competitive performance.

I expect a larger part of it is there's no justification for Qualcomm to develop such a SoC, because it already gets the sales.