Built 904 Transmission
it looks like most builders list similar spec competition units in the 3K range so i'd use that as a starting point.
that thing seems like it's le boeuf which kinda takes most of the unwashed masses out of the market, leaving a more serious crowd-- which could be a good thing, or a bad thing. generally somebody spending that kinda dough for a trans is having it built specifically for their application, especially the torque converter so they may not see value in coughing up a bunch of dough for something that they're going to have to modify for their needs.
if you have a detailed build sheet that contains specs and the shop that did the work is a known entity that can certainly move the needle. but used racy stuff is usually 50~60% off list.
GLWTS