In my opinion, they really are not worth the extra amount, sonically.
I would say the same in regards of comfort, given so many reports of hassles around, and need of refitting, but the thing is that even a JH13 sounds small, and like a IEM. Back then when I owned one, others agreed with me that it sounded slightly smaller than a Triple.fi 10 Pro. Also it wasn't perfect, the midrange wasn't lively enough, detail retrieval was good, but not electrostatic-like; the highs were very slightly metllic. Best iem I tried, regardless. But still in the same tier with the Apuresound ER4P, UM3x and the likes.
Also, using the JH13 out of a DAP, which is the way it is intended to be used, is really limiting it. Out of a 1500 usd home rig they sounded much better, tonally and detail-wise... but still small, and still less special than a audiocats-modded Babystax setup out of the same source. Impossible to pretend that it could compete witht the bigger guys, yet, back then, many people used to say that.
Also very fragile.
Well that is a subjective thing and not all Custom IEMs are the same or even similar for that matter. I have a universal fit version (Company is TBA) and it is a significant upgrade over all universal IEMs I have tried to date. The sound staging is rather large as well. Reminds me of the IE80s massive sound stage but with a lot more detail. With this type of sound stage I am more apt to think I'm wearing full size headphones opposed to IEMs. Plus the portability and comfort are better than a full size headphone. YMWV.
Edited by lee730 - 8/6/12 at 9:06pm