I heard the $4000 Focal Utopia Headphones yesterday

Is Berylium hazardous? More so than stuff in other headphones?

If I was going to spend a lot of time listening only to headphones I would consider spending 4K if seems worth it.

My audition was short but listening to some well recorded familiar tracks not sure I heard the value proposition with these. They cost almost 20x more than my most expensive current phones.

I don't know the specifics but under certain circumstances beryllium is very toxic.

OK that would seal it.  No beryllium headphones for me then. :^)

I have worked extensively with using beryllium-copper alloy in various components and don't recall any special handling procedures in the factory for such materials. We used them in designing the casings for components that were exposed directly to salt water in under-sea telecom cable applications. I don't think anyone uses pure beryllium in any consumer product applications. I have little doubt Focal has done enough research to make sure it is harmless. This is of course all moot (for me) since I would never ever pay that much for headphones unless that was the only method I could listen to music for the rest of my life....