iPad is the cheap one, the 10th generation is $449 vs $599 for Air. And the 9th is still being sold for $329. Lots of people want a basic tablet for browsing and don't need power for pseudo-laptop.
In another year or two, the M1 will be 3 generations behind. At that point Apple might well just eat a small BOM cost difference. As processes shrink the previous nodes get cheaper.
The iPad Mini has A15 Bionic.