Bunch of fancy cameras (same as every other flagship smartphone) and following the unwritten "thou flagship shall be expensive" rule that has little to do with silly things like hardware cost.
Somewhat surprisingly, Lenovo/Motorola here has some of the more affordable mainstream phones (200€-ish for the G56), beating other Chinese brands that played around tiny margins and got hit even harder by memory prices now.
There will be more devices from Motorola providing official GrapheneOS support including budget devices. It has to start from the top down since Qualcomm currently only provides the security features we need for flagship Snapdragon. We also still need proper long term updates for budget devices.