I would agree with you that finding this piece of information is difficult.
I think you want to contuse IDEA directly at 1 800 99 4332. I have found the staff there quite helpful when I have been confused by something online. You could also do the live chat. Remember that this forum is not really handled by IDEA staff, but by other certified trainers, so it may be faster to ask IDEA staff directly.
I took a while to see if I could access the info myself without calling, and found that there is a tab to look at professional discounts, but they take you to the IDEA store, where you can buy CECs, some of which are discounted.
I also found an outside ‘coupon code’ page that suggested you could get ACE discounts by signing up for a temporary free IDEA membership, buying your ACE product, and then immediately canceling your membership. Not really ethical. Kind of like buying a dress for a formal and returning it after wearing it…. I have no way to know if trying to maintain more control on how discounts are used in any way effected how IDEA and ACE are handling them, just something that surprised me.