YES, CUSTOMS ARE VERY OVER RATED!!!
There is a big diminishing returns beyond $400 IEM's especially with no major tweaks/upgrades in gear. I understand the extra drivers and intricacy to make a JH16 but from an upgrade SQ standpoint it is not worth more than $550-$600.
In addition, it is my opinion that as you put more and more drivers into a housing there is a much larger margin of error for 100% repeatibility in the sweetspot for the sound sig. There is some marketing hype on JH website about why customs deliver the purest sound due to the perfect fit but that is only true if you get the perfect fit which is very difficult to do with regular consistency.
Conversely, universals will always provide a more repeatable better fit just due to the better tip options. A comply tip or a tri-flange will forgive all differences in ear anatomy from one ear to the other. A hard acrylic custom tip either gets it perfect or doesn't. There is zero margin for error. JH matching frequecies for drivers on each side is meaningless unless a perfect fit is achieved. Ety matches drivers and the triflanges will assure you get that perfect insertion/depth fit. A custom acrylic can never guarantee that.