I heard the $4000 Focal Utopia Headphones yesterday

Very nice. Very expensive. Beryllium drivers.  Reviews a bit hyped I think. Who would pay that premium otherwise? Not sure I could live just with any headphones still.

I find it a bit disconcerting to have Beryllium so close to your brain.

Cheers George
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.

Is Berylium hazardous?,  An old engineer friend recalled that during the second world war he worked for Elliot Automation in England building the Lancaster bombers. Women were handling beryllium plated instrument parts bare handed, then falling of their stools dead.

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

I personally wouldn't get too paranoid about it, The women I referred to worked in an electro-plating plant handling and wiring components all day long. There are many potentially toxic materials in all our lives that are potentially worse. The beryllium domes used in transducers are always covered often due to their fragility as seen on Yamaha NS1000 monitors. Beryllium may be toxic if handled directly over extended periods but it's not exactly radioactive. Some people swear by beryllium drivers and some swear at them , at the end in this hobby it's all about subjective implementation and I'm certain Focal have done their homework and sound wonderful as they should for the money..

I belive beryllium is dangerous during the manufacturing process but left alone is stable.  It is brittle and can be poked with a finger which is  why there is a metal grill over the beryllium mid/tweeter of my TAD's.   
Beryllium is toxic, period. Skin contact usually only raises a rash, but forming the stuff is always left to specialty shops, which is why you can't just buy some to play with. Beryllium copper alloy is mostly copper, which is why it is safe to use.
Don't know if they are worth a try at $4000 but I have a pair of Shure SE846 IEM for $1500 and I have never heard anything even remotely as good in an IEM.  These IEM sound very close to the very best open back cans I have heard and have incredible noise reduction because of the great seal with memory foam.
Beryllium dust is deadly but as no one will be subject to beryllium dust from a set of headphones I think you are good. I don't suggest that anyone should extract the beryllium diaphragm, drill it to create a cloud of dust and then inhale deeply :) other than that you are safe.
For far less yhe Stax Electrostatic head phones are magical 
There are many sub $1500 headphones that are exceptional. $4k for headphones is a rip off IMO.
Don't jump to any conclusion. If you have the means and are interested, give it an audition and decide if it's worth it to you. I did just that, after half an hour of listening to music of different genres, I bought it. And I already own the $3,000 Hifiman HE1000. Substantial step up. 
Lots of paranoia around here. The effect of any poison is dependent on the specific compound involved and dose along with the frequency and duration of exposure. For example, many old houses contain asbestos, but there is no particular risk if the material is stable and not disturbed. It is when the material is removed that things become hazardous unless special precautions are taken. 

Here's a link to the CDC web site on beryllium: https://www.atsdr.cdc.gov/csem/csem.asp?csem=5&po=15

And, just to make everyone extra paranoid, don't forget that apple seeds contain cyanide and solanine can be found in potato skins.

One things for sure that sexy carbon frame cost a small fortune to make,
not to mention that is lighter and stronger then steel.
Post removed 
Parts Connexion is having a significant sale on Stax headphones.

Pure Be is diff. than alloys. Pure Be is brittle as hell. Break it and the dust is toxic if inhaled.
I’m not a big headphone guy at all.  The hifi man, and audeze headphones have always sounded nice to me, but the Focal Elear and Utopia are just magical.  I’m so tempted to buy a pair of the Utopia’s...  never thought I’d say that, as even a $300 pair always seemed like a waste to me.