Again; the code @cclarry gave me, the one starts with "THANKS", worked for me on my second purchase with my only 8dio account.
So, it's one of these possibilities:
Larry hacked into 8dio servers and created a code that works multiple times.
8dio is thankful to Larry for making them earn a million dollars (on this forum alone), and gave him a special code.
There was a glitch on 8dio's website.
There is a special promo going on for existing 8dio "Advanced Drum Series" owners.
The drum was AU$20 instead of US$20 for a brief period of time.
Elvis didn't do no drugs.