Please read the Player Guide section about the Bazaar, young Wizard. The Bazaar is solely stocked by what other players sell there.
Wizard101 has a Bazaar! Olde Town is the place to be - there you will find the Bazaar. Players are able to sell their extra items to a new shopkeeper named Elik Silverfist. That's me on the left! I'll pay you the value in gold for the item based on supply and demand. If I already have lots of the item you are selling me then I will pay you less gold for yours. If I'm low or out of stock on the item you are selling, I will pay you more gold!
This also means that if I have lots of an item already in my inventory, I will sell it for a lower price, and if I only have a few, or one, I will sell the item for a much higher price! All prices are based on my current stock of items, so shop often for that special bargain, young Wizards! And don't worry, if someone sells an item on Wu Realm, and you're on Pixie, you'll see it in my inventory - I've got all the Realms covered!