I've seen various teardown estimates with a rather broad range. But anyway, when I ran various numbers a while back, I found the MSRP markup numbers to be really similar across the 8, 8 Plus, X, XS and XS Max. It was about 2.8x across the board.
Given that the standard deviation on gross margins has been about 2% for the last decade, a ±5% margin on a product seems reasonable. After all, regardless of the component costs, it's a safe bet you'll have a US price for a standard model that ends in "99," and a certainty that if not that then it'll end in "49."