Edited by: Tau Cabalander on 11/08/2011 17:27:16
Originally by: RaTTuS
it's because they all appear in the extras part - to save the exploits that where there when they came out
Extra materials don't have any waste, nor are they reclaimable via reprocessing.
All structures requiring PI materials were reprocessable before the NPC sell orders were removed from the market. This resulted in people buying some structures cheaply from NPC, reprocessing them, then building more expensive structures with the parts and selling them back to the NPC. CCP finally stepped-in, far too late, and changed all the materials on structures to be extra.
You can do P.E. research to reduce build times though.