There are reasons why things are little bit more expensive to make. And those add up quickly. The flexible OLED panel is more than double the BOM cost of rigid OLED even at the scale of Apple. For Apple that is ~$150+ of RSP increase form a single component. It is not only just being rigid, but they are also a higher quality panel. People often only look at "spec" on the surface without actually going it into details. Add up the cost of iOS ( $10 on accounting basis or $30 for RSP ), Face ID etc you are looking at $200 RSP extra already without going into any many other differences. Of course the main thing being Apple has a gross product margin of 60% compared to Xiaomi at ~10%. ( I think they raised this to 15%+ due to operating cost being higher outside China )

It is also worth remembering. Hardware is insanely cheap. Comparatively speaking. We talk about moore's law ending because of higher cost of making chips, at the same time we keep making dozen of billions from stupid social network and ads. The number by comparison are often comical. The cost of a product are now mostly driven by software when Apple are still giving iOS update to a phone first released 6 years ago.

It might also be worth noting, the entry level iPhone, iPhone SE, has faster single thread performance ( Very important due to Amdahl's law ) than the best flagship Android Phone on the market. You have to price this in somewhere.