Since it's like a premium version and it's not modifying game files it gets by somehow. I personally hate Zygor's guides and always have, it's just personal honestly. I understand some people like his guides and have no problem paying for them but I personally hate the idea of charging someone for an addon that - as this post points out - has plenty of bugs in it. These were fixed last week and if I'm paying cash for an addon I want that addon bug free and not causing a hassle and taking my time away when I could be doing a better job without an addon at all.
The part you need to understand too, is that the Zygor addon doesn't use an App like TSM to update many times per day your auction value. When i bought the gold guide i remember that i didn't understand much either, the results were random and from items i can't make much gold with. It just scans the auction house based on their most recent value update which can be days and days ago.
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