But that would mean when you equalise RAM and storage the 15" Air would be more expensive than the 14" Pro, despite lacking a lot of the features. While Apple are anything but generous with pricing, they do follow a sort of internal logic for these machines. In the absence of any other feature/ justification, a larger screen variant will be a +$100 or $200 premium over the smaller variant, depending on the product. 8 -> 16GB RAM always costs $200, regardless of the context (i.e. what sort of RAM is in the computer you're buying) and 256 -> 512GB storage is again always the same $200.
Applying this to the 13" Air, a 16/512 15" Air would be $1,899 with 10C graphics, just $100 off the base 14", that's more than close enough to start getting people to mull over whether the MBP would be a better option for a better display, more power, more ports and better speakers.