Apple’s quarterly results don’t specify which iPhone is making how much money, not does the ‘aggregated group profit’ (which is big news) pushing earlier stories off the front page mean it’s incorrect.
I hypothesize a situation where the iPhone 8 and 8+ (and the still selling earlier versions) which have R&D costs that are mostly, or completely for the earlier versions amortized unlike the X which is largely new technology and which accordingly will have much higher R&D cost apportioned to each sale (1)
A new mass market phone making use of (at least part of) the technology and style pioneered by the X (the 9 series) would almost certainly make Apple more money than the X does (2)
(1) yes this is bean counter speak, but that doesn’t invalidate the logic in and off itself.
(2) I’m not saying that the X isn’t profitable, just that profit could be increased further with a different product (which is all a bean counter need to justify replacement of a product).