I played as a custom race with Thalan tech tree. Halfway through the game, I researched the neutral alignment. This give me a discount in direct purchasing. Then I researched the neutral unlocked tech Hyperion fabrication that further enhanced that discount. And I was shocked to see that my discount was now 100%, essentially zero.
That should have been 50%. 25% from being Neutral, and 25% from Hyperion Fabrication.
Are you certain, that you didn't have the 'Corporate Corruption' random event at one point? The evil option for that event grants a bonus to your Purchase Now Reduction ability. It's the only way you could have reached a value of 100%.
PS: I preferred the way this ability originally worked. In DL and DA, it reduced the the amount of interest you pay each turn. With a value of 100%, you don't have to pay any interest at all. The cost you have to pay upfront, however, stayed the same.