I don't have the PS2 version of Origins but, if I remember correctly, it was ported from the PSP near the end of the PS2's lifecycle, right? To my knowledge, games that were manufactured during that time and after sometimes had thinner, almost paper like slipcovers, manuals and inserts.
For example, the three Fatal Frame games for PS2 were reprinted a few years back. When I bought a reprint of the third game in that series, I noticed the reduction in quality that you described. I later bought the original print from 2005 and found that the production quality was much better and identical to other high quality prints. The case was original, too (whereas the reprint lacked the memory card slot in the case, the original did not).
Could this have been the case with your copy of Origins?