I used to have a Cynic shirt like, a decade ago. I actually got it at Spencer's, lol. I wish I kept it, I've seen it go on Ebay for over $100.
I still have an old-ass Hypocrisy shirt with only red and white print... has Jesus bloodied up in a pentagram, and I've NEVER seen or even heard anything about this shirt, ever. I bet if it was still in decent condition, it'd be worth a fortune. We used to really want those Isengard shirts, too, but I think they were reissued identically the same, thus ruining thier prestige value.
The only shirt I could never find was a Draconian Times shirt from Paradise Lost. That album was godly.