Let me break this down easy... (all numbers are made up by me)
Tech's Anghellic release could have been limited at the time because of money constraints to release 100,000 copies of Anghellic. Let's say 20,000 of those are sittin' on the shelves, and the other 80 were eaten up by hardcore fans...
Then Tech releases AP and releases 200,000 copies, and 18,000 are purchased and the last 20,000 of Anghellic are bought with absolutely no marketing push whatsoever... The decision is then made to reprint Anghellic discs with extra tracks so that the album hopefully matches the sales of the AP album and also gets a few more fans to buy the next album..
Having an undiscoverd album available for re-release is basically like having an entire album made and sitting in a closet while you make new shit. Just because it didn't just recently come out of a studio doesn't mean that it can't sell just as much, if not more, than AP.
I'm pretty drunk right now, but I think this gets the point across, and thats not even mentioning that the Anghellic album has the 3 extra tracks on it, which assures that people who have already payed for Anghellic, will pay for the same album twice for a few extra songs.
Re-releases are a good thing for uneducated consumers, and the artists. I think more bands and artists should push their really old shit in the form of re-releases. The more shit you have out there the better the chance is that I can find at least 1 or 2 things that I like by you..