Plus, if Apple can afford to put an overclocked / high-binned TSMC chip in the lower-cost iPad but has to put a low binned i5 in the Air doesn't that say something about the relative economics / yields.
For what it's worth I have a Core i7 1065G7 and it's decently fast but gets very hot and definitely needs a fan (which the iPad doesn't) and has good battery life (but not as good as the iPad's).
The advantage still seems to me be to be very strongly with the Apple parts.
Potentially. It probably also says more about the relative product positioning of the iPad Pro (high end, max performance) vs. MacBook Air (slim, light, and by requirement slower than the MPB so that the products are correctly differentiated).
The point is you're reaching. The A12 is a great part. TSMC is a great fab. Neither are as far ahead of the competition as Apple's marketing has led you to believe.
The first i7 from apple starts at ~1.6x the price of the ipad pro in the macbook air 2020, yet the results of comparing the a12z with that show that, performance wise, nothing really changes: https://browser.geekbench.com/v5/cpu/compare/2626721?baselin...
I'd suspect the reason is that these benchmarks are long enough, that the Intel CPUs just end up completely throttled down after the first ~30-60s, while the A12Z does not.
Either way, the trade-offs here have multiple axes, and honestly die-size is not something I as a user care about. I care about performance / $ and battery life / $. The A12z seems much better along these two axes than either of the Intel CPUs in the Air 2020.
To find something competitive in terms of performance (but worse battery life) from Intel, one does need to go to the Core i7 1065G7 that you mention, which delivers approximately the same performance as the A12Z: https://browser.geekbench.com/v5/cpu/compare/2627162?baselin...
However, the first machine with that CPU is the Macbook Pro 13' 2020, and that starts at ~2x the price of the ipad pro. From looking at the upgrade prices, the cost of that i7 alone might be by itself ~50% of the whole ipad pro cost, or larger.
So while you are right that these two are comparable in terms of raw power, I doubt they are comparable in terms of performance/$ and battery life/$. Without knowing the exact costs of each we can only speculate. If that intel i7 is 2x more expensive than the A12Z, then perf/$ would be half as good, and since raw battery life is worse, the battery life/$ axes would be twice as bad.
The reverse is most likely true. The macbook has a bigger aluminum body to absorb and dissipate heat. In addition, it has an active cooler with heat pipes to conduct away that heat for ejection from the system.
You keep coming back to that citation. It's more than a little spun. The parts have comparable semiconductor process (Intel 10nm vs. TSMC 7nm) and die size (146.1 vs. 127.3 mm2). But the the A12Z in the iPad is running as fast as Apple can make it (it's basically an overclocked/high-binned A12X), where the Intel part is a low power, low-binned variant running at about half the base clock of the high end CPUs, with half the CPUs and half the L3 cache fused off.
A more appropriate comparison would be with something like the Core i7 1065G7, which is exactly the same die and can run in the same 12W TDP range but with roughly double the silicon resources vs. Apple's turbocharged racehorse.