Spectre771, even though AT 3, 4, 11 and 12 could theoretically be available for players, we always assumed that it was not available simply through normal means because of the description mentioning animal hides (even though, for AT 11 and 12, it mentions armor "and" animal hides) plus there is no price listed for these three armor types anywhere in the official RM books.
YMMV
Thank you Ecthelion. Out of our gaming group back in college, 7 of the 9 players were all Martial Arts members (that's how we all met), and we reasoned that Rigid Leather was listed as a type and we knew it existed in the 'real world' so we used it. Oh well, going forward, that's something we're going to adjust in the game.
I also allow the "high level Leathers". And I know there is no price. I allow people to add materials like Giant Crab Shell or the like to the construction of armor. This must be done by a special leatherworker and a series of check be done to ensure that the armor was created correctly.
One character has a set of Full Hide Plate made from the hide of a lesser Demon Lord. He wears it for three reasons. First, it gives greater protection due to the material. Second, it give an intimidation effect. Third, it attracts demons like a moth to a flame. Yes, the character is psychotic, but that has nothing to do with the armor.
The armor is considered priceless. But we used the time to create armor for the less leather, and I made the creator to make a Crafting check daily.
-BP