Dunu Luna uses a bespoke driver platform developed in-house with a pure beryllium dome, which is both extremely rare in the industry and quite expensive to manufacture consistently to tolerances. It’s also got a shell machined out of titanium. Do they cost anywhere near $1600 in materials to produce? Of course not, but Luna and the Eclipse driver platform they designed for it haven’t been a real commercial success for Dunu. Even the Zen Pro which uses the same Eclipse platform with a cheaper Mg-Al dome didn’t rake in the margins it would need to be considered a real success. For their cheapest Eclipse platform IEM Falcon Pro, Dunu went out and found an existing OEM driver which had some of the same features of their Eclipse design, allowing them to sell the Falcon Pro near Kato prices.

Sennheiser’s IE900 shares a driver design platform with the IE600 and IE300, however the drivers in the IE300 use different voice coils and are manufactured to looser tolerances in China, whereas the IE600 and IE900 drivers are made with higher grade components to tighter tolerances. In addition, the IE900 has a fully machined housing with machined Helmholtz resonators internally for tuning, which is expensive; even the Chinese IE900 knockoffs with shittier machining quality run $270.

The actual drivers in the vast majority of IEMs are either off the shelf OEM components or custom variants of OEM designs, and the drivers in most single-DD IEMs cost less than a dollar a piece when purchased in bulk.

There’s a huge step up in costs from using a drop-in driver and tuning with damping filters to using custom designed drivers ordered from an OEM combined with acoustic shaping in the IEM body/nozzle, and another huge step up in costs from there if you want to actually design and build the whole thing, or nearly the whole thing, in-house.