Nope, they don't.
While it may seem that things are being duped, they really aren't. Thousands of accounts get hacked on a daily basis. Any valuable BoE's / cagable pets found will be sent to another account to be sold on extremely quickly, thus the low prices.
The original items are then restored through Blizzard's own item restore system, once the account owner realizes that their account has been compromised. By buying any of these items, you are basically motivating these types of people to hack more accounts and sell gold.
I noticed this during the week. Spectral Tigers and Soul-Traders started popping up for as low as 90k, with 5-6 others under the 100k mark. Tried to talk a guy into 75k for the soul-trader (I'm cheap, and it's just a pet) but he wouldn't go lower than 90.
And I saw, and behold, a pale horse: and he that sat upon him, his name was Death; and Hades followed with him. And there was given unto them authority over the fourth part of the earth, to kill with sword, and with famine, and with death, and by the wild beasts of the earth.
ye i have seen alot of them lately aswell, but ill wait to buy them now thay are duped thay will drob in price super fast
dont think anything can happen when buying them - i got pritty mutch all tgc mounts and gotten them all via gold, meny of them form the same lvl 1 dude - first i buyed 2 mounts for 175k off him he asked what other mounts i missed i told him, he said wait 20 mins i transfer them - 20 mins later i got another 5 mounts for 500k - had them for more then a year and nothing has happend to them
and i thought i got mine for cheap , i put all my gold on it (100k)
is this a good price ??
If you buy a duped item and then sell it instantly for a massive profit, you won't get banned. Neither if you buy stuff from a hacked account.
So buy, buy, buy some pets, save them for a while until the dupe is fixed, then start earning some serious cash.