Stax sells low-mechanical-quality plastic headphones for over 1000$, Denon sells Chinese slave-labour for over 1000$ (despite aesthetic appearence much less carefully manufactured and assembled) and let's don't start with Grado and their manufacturing processes...
Leona is manufactured by a Japanese company (Asahi Kasei) and propably costs only a few $/kg as a raw resin. It's a high-quality material and available in many different variations with different mechanical properties but it's most likely much more durable than ABS.
The economic value added comes from the molding process. The "mold" (I'm not sure about the correct technical English term) for these precise and complex shaped parts is machined from highly-skilled craftsmen and easily costs >100,000$ each. The injection moulding machines are also quite expensive (like ARBURG - Herzlich Willkommen bei ARBURG Deutschland - Spritzgießmaschinen, injection moulding machines, Spritzgießmaschine, molding, machine, Spritzgussmaschine, Spritzgussmaschinen, ALLROUNDER, robot, Handling, Kunststoff, plastic, plastics, MULTILI
) and have to be maintained carefully (also by trained craftsmen) and the parameters have to be taken care of. in Germany these craftsmen visit special "technical colleges" to learn these "crafts" - they're not "trained-on-the-job" (although Sennheiser has special practical education programs, too). It's entirely different from the manufacturing of a Chinese OEM.
I think it's great that Beyerdynamic and AKG didn't outsource their mid-class consumer production (although I'm not sure what AKG is up to) but just take a look at the assembly of the drivers - the HD800 is on a different level (just like the similar priced T1) and the K701 doesn't have it's build-quality, either.
I'm not a big fan of the optical appearence of the HD800 myself, but their effort (12 engineers worked for 2 years alone on the HD800 development - especially vibration-simulation instead of simple trial&error) and experience in designing and manufacturing professional audio-equipment is unique.
I hate their consumer-crap, but the HD800 is entirely different. I'm still not sure if I take the HD800 or T1.