It's the retailer's choice if they're willing to accept lower or even no profit and use the iPads as loss leaders. Even now, there are minor discounts being offered for the 2017 iPad. I wouldn't be surprised if we see it on sale for $279 down the line.How is it not? Brick and mortars dropped the price of the Air 2 to $299 all the time. Apple instead decides to kill the better tablet and give you an inferior design.
Besides, until the minor refresh late last year, capacities were lower at 16GB and 64GB. I'd take the $329 2017 iPad 32GB over $299 Air 2 16GB anytime. The display on the Air 2 is a nice bonus but having just 16GB storage? That's quite restricting even 3-4 years ago.