New account, limited resources, perhaps all they had on hand to dupe. Probably only on AH because the lesser quality wouldn't sell through trade channels, where most dupe items have probably been sold until now.
Sell all, collect 12 million gold, buy a better item, dupe seven times, repeat.
I think this might be the product of the glitch that has been going around; A lot of people have been reporting multiple of the same items dropping, down to the name and exact stats. It seems to be in rare cases but I don't think this is actually someone duping.
This is not a case of elites dropping 2 identical items, the "dupe" ( if that's what it was ) was most likely AH based, like the cancel buyout and buying for bid hacks earlier, which involved editing client side info and WORKED.
I say this because the items all were posted and had expiry times IDENTICAL, so I guess some1 has found, AH exploit number 3.