I heard the $4000 Focal Utopia Headphones yesterday

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..