It also depends on what exactly Gartner classified as "Ultramobile (Premium)", which they apparently counted towards the "Total PC market" (262 million in 2017). Which one comes out ahead depends on the relative share of Windows 10 tablets vs. iPads in that segment.

In any case, that still puts Metal and DirectX in the same order of magnitude.

Don't know about any statistics that cover specifically that segment, but when it comes to new device shipments, it has been reported that iOS + macOS surpassed Windows + Windows Phone already in 2015, and it is estimated that this trend has continued since then.

PCs. iPhones are very us centric ... the rest of the world dominates unsurprisingly.

That's probably a good question. Those who are actually pushing the hardware in both camps are most likely the minority, as opposed to those who are working with glorified web views.

But AAA on a Windows desktop commands $40-60, whereas AAA on mobile commands < $8 +/- scuzzy IAP schemes.

This list[1] is quite a bit different looking from this list[2]

[1] http://store.steampowered.com/search/?filter=topsellers

[2] https://www.apple.com/itunes/charts/paid-apps/

Over a billion iPhones have been sold, and a couple billion Windows PCs. Not quite "two orders of magnitude".

Are you so sure about your numbers there? What's your evidence?