Since the very first PTR of WoW prices have been enormously, unbelievable high. There is no good reason for it. Players simply put things up for huge amounts. If you want to change that publish your things at low prices. Change could happen slowly and at least you'd be helping. I post things for super low sums on PTRs to try and help people test things.
^ this. And less people playing is a big factor as well.
Not much Blizzard can do really. Also, their focus on patching isn't to balance prices or the economy, they're patching mostly gameplay content. Most AH-related patches have been aimed towards improving the UI or functionality (more search parameters, etc.)
if the root of your complaint is that the equipment you want isn't available to you then why complain about the AH instead of just request that you have unlimited resources and/or can make your own equipment on PTR?