The flex circuits are actually pretty high-tech and not cheap nor easy to do except for PCB manufacturers that are specialized in it. This hardware is pretty impressive in my view; it's not as impressive as a modern smartphone, but it's a lot more impressive than most other consumer-grade stuff I've seen, especially because of the PCBs used here.
The big differences between this and smartphones are that smartphones use a lot more chips, most of them very high-density BGAs, and much more powerful ones (esp. the CPU), and have to worry a lot more about heat dissipation. Smartphones probably have more layers in their PCBs too, and that's expensive as well. But the PCB assemblies here I see in this teardown are not simple or cheap. Most consumer electronics try hard to minimize the number of PCBs, and to avoid any complex shapes or cutouts, and definitely try to avoid flex connectors.
Flex circuits are not that hightech nor expensive. IIRC the per square inch price of single layer kapton flex PCB is comparable to your traditional four layer FR4 board.
On the other hand large amount of cheap(-ish, as it tends to include even high-end AV receivers) tries very hard to avoid FR4 and multilayer boards in general (apparently in high enough volume making four times larger board than required and the huge setup cost for THT assembly autamation makes economic sende)
I think that's probably true, especially considering that the light has about all the hardware of a modern smartphone inside, minus the screen.