Munchkin Dungeon: Dungeon of Superior Shopping

The Dungeon of Superior Shopping is a promotional item from Steve Jackson Games that can be used with any Munchkin expansion that contains Dungeons. This item is larger than other Dungeons (6"x4" instead of 4.4"x3.3") and is meant to be kept separate from them. It was handed out as a promo item during the 2015 International Tabletop Day. Its text reads:

When a Portal adds a Dungeon, any player may choose to put the Dungeon of Superior Shopping into play instead of drawing a Dungeon from the deck.

While in this Dungeon, everyone can purchase not just levels, but Doors and Treasures!

On your turn, you may discard 300 Gold Pieces worth of Items to purchase one face-down door, 600 Gold Pieces for one face-down Treasure, and 1,000 Gold Pieces for one level, as usual.

When the Dungeon of Superior Shopping is discarded, place it back in the box. The sale of a lifetime only happens once a game, after all.