It’s the expense against expected return. THX 1138 is not really likely to make a huge amount of money in sales, either version, let alone having two versions out there.
I bought the original VHS release back in 1988. (I know this because I worked at Reader’s Digest at the time and they were selling the trilogy set in their employee store for $12. I couldn’t pass it up.) Until I read this thread, I had no idea I was sitting on a potential gold mine.
E-bay, here I come!