Refund

Refund is a badge in Paper Mario and Paper Mario: The Thousand-Year Door. In Paper Mario, it is located in a chest box outside Koopa Bros. Fortress. Mario can blow up the wall in the right of the lowest floor in the right of the fortress with Bombette to get it. It costs 1 BP to equip. When equipped, Mario and his partners can get 75% of the standard prize of a item if they use an item in battle, rounded up, except that for a Jelly Ultra they get only 113 coins. In Paper Mario: The Thousand-Year Door, it can be bought from the Pianta Parlor for 34 Pianta Tokens, and dropped by Bandits. It costs 1 BP to equip. When equipped, If Mario and his partners use an item in battle, they will be given some coins back. They'll get 75% of standard sale price with the first badge, and an extra 5% with each subsequent badge equipped.

Merluvlee's prediction in Paper Mario

 * "I see...a Refund Badge. It's on the far side of the Koopa Bros. Fortress. Use a Bomb to blow a hole in a wall, then go outside to find a part of the castle that juts out into the water. The treasure chest rests there, and the Badge lies within it."