Remember when expensive headphones, let's say anything over $100, were never big sellers, and only audiophiles bought them?
That's no longer true--judging by the number of Beats by Dr. Dre headphones I see on the streets and subways in New York--pricey headphones have reached the mainstream. That's radical. Bose did pretty well with its QuietComfort noise-canceling headphones long before Dre jumped into the headphone business, but the Beats stand out in a crowd.
The reasons for Dre's success aren't purely based on sound quality, it's more that the other manufacturers' headphones sorely lacked any sense of street style.
Dre targeted younger buyers, and turned them on to thinking about sound, and made sound cool. Dre's sound didn't do a thing for me, and that's fine, they weren't designed to bring out the best in acoustic music or jazz; Beats were more about the beat, and visceral, high impact bass.
As I've said many times before, sound quality is a subjective call, and there will never be a headphone or speaker that everyone agrees sounds great. There's precious little consensus about what constitutes "good sound." Some of us love tube amps and some like solid-state. There are hard-core vinyl guys, and there are many times more who listen only to digital recordings.
I'm happy to see legions of Beats buyers in their teens, 20s, and 30s loving the sound. They're passionate and loyal, but as they age the chances are their tastes will evolve, and they'll start to consider headphones and hi-fis with a different sound. The price barrier has been broken, so they'll be more likely to consider dropping serious cash to get good sound than the generation that came before them. Who knows, some of them might even become audiophiles.