The Galaxy S9+ is Samsung's costliest device to produce to date, but it's still less expensive than the iPhone X. Among the most expensive components integrated in the Galaxy S9 there are the Exynos 9810 SoC, the AMOLED screen and the camera setup.
https://www.notebookcheck.net/Samsung-is-spending-US-379-5-to-produce-a-Galaxy-S9.289884.0.html