It's expensive and difficult to make
I don't think this point has been hit hard enough in this thread. The expenses to make a box set like this are not limited to CD-printing and booklet-printing. There must have been a crapload of research that went into this. For example, the question I just asked about the music in Way To Eden. I'm sure Jeff Bond went with the best info he had, when he wrote his book, but it seems like there's more to the story given the relationship between one of Adam's songs and the score-cue I mentioned. Someone had to track that down, and that was work. (Possibly it was delightful and interesting work, but effort was still put forth.)
That's one example. I'm sure there were dozens of similar cases. At a minimum, written records of recording sessions had to be examined, and possibly cue sheets for every episode (even ones presumed to be track jobs), and possibly the surviving composers interviewed. That's just to gather info. There was also the work done on the re-mastering, which is not something I know anything about.
La-La Land was in it pretty deep, from an expense standpoint, before they ever got near being ready to print a single disc. Maybe a lot of people contributed their effort and knowledge, because it was a labor of love, but there were still expenses. The price we've been quoted seems quite fair, given the effort involved. (I value the Jeff Bond booklet pretty highly, after reading his book.)
I'm sure there has been price gouging on other TOS stuff. This doesn't seem to be an example of it, though.