Because of how quickly you can fill your graveyard with the cards you actually want in there while drawing into your game-winning combo pieces, Wizards of the Coast decided that this card needed to be banned in most formats. It's not banned in Vintage, however, where there is a much smaller ban list. So, because of decks like Dredge that utilize the Graveyard, it's still incredibly valuable.
In fact, Bazaar of Baghdad is one of the most expensive cards in all of Magic: the Gathering. If you're lucky to own a copy, congratulations!
Have you ever played Bazaar of Baghdad?
~ Phoenix <3