What Apple did differently, of course, was to introduce the iPhone X in the first place, at $999.
Up until then, they had introduced each year’s new iPhone as their premium, mainstream offering, whilst discounting the older models from previous years.
But when the iPhone X became their top selling phone..
The iPhone X continues to be Apple's top-selling smartphone
The iPhone X continues to be Apple's top-selling smartphone according to the company's latest quarterly financial…
..they were naturally keen to try to keep $1000+ as the new mainstream price, if they could.
The X was presented as a foretaste of future technologies — and that’s how they justified its extra-high price tag. But by the time the XS came out, those technologies (and the all-screen with a notch design) had become the new normal — and yet they maintained the $999+ price tag.
The pricing of the XR was also significant — because it was priced at $749, not at $699, like the new iPhone 11. This, I suggest, is precisely so it didn’t become too attractive an offer and outsell the XS. They wanted their top seller to be the $1000+ phone.
Also, you’ve made an error:
Here’s a timeline of Apple’s iPhone announcements since 2017:
Sept. 2017: iPhone 8, $699
Nov. 2017: iPhone X, $999
In actual fact, the iPhone X was announced in September 2017, at the same event the iPhone 8 was announced at.