Very impressive bass response out of such a tiny device. The mids and highs are on point, clear and precise without being screechy or fatiguing. Sound quality is just like having a full set of high end cans on your head, except you don't... The only down side is there isn't much space to the sound because the drivers are inside your ear.
They can be difficult to get in your ear right though. Ya have to find the right tip and jam em in your ear enough so they seal. If they don't seal then you get zero bass. The swappable filters inside the nozzle are handy for tweaking the sound to your liking. It's not a gimmick, they do what they say.
I found a seller on ebay listing them as a display model for about $800. When I got em the box had never been open so I lucked out on that one.