^ I don't see an adapter anywhere on there; just custom cables. $50 is crazy! That's like those WBT RCA plugs you see on expensive audiophile cables.
I bought two of the Sony's linked above, should be here in a couple days.
I would have thought someone like Neutrik, Switchcraft, or Canare would make quality versions of these adapters, but I couldn't find any. It must not be worth it to them.