I agree with
@mrk, although I think it's bit of a perfect storm. I think there's been an explosion in the headphone audio space over the last 15-years where demand and commercials have gone through the roof. I think some of it is actually driven by increased online presence and gaming with online, streaming and multiplayer all becoming the norm. All added to the explosion of music streaming etc. In the US particularly you've had the likes of DROP, Apos, Schiit all come about and deliver bargains where it be things like the HD 58X/6XX, or Gremlin for $120, or the first Schiit products for $99 each. All aligned to Fiio, SMSL, Topping (could also chuck in a few brits like iFi and Chord here) etc. pushing the boundaries lower and lower in price. Even to the point where traditional PC audio companies like Creative have had to adjust, or gaming headsets have matured to become 'good' becuase they realised basic stereo quality was important.
But given you can get a set-up like a Fiio K11/R2R, or HD 560S for just over £200. It is ridiculous value and there's loads of other examples. It feels like one of the few product areas where the greed hasn't gotten a hold in the way Nvidia has ruined their GPUs, or memory companies like the 257% increase in profits and so on. So we should probably shut here for fear of them noticing!