Item rarity levels

1. Virtual Auction vs In-Game Auction (Virtual Economy Gamification Tips)
2. Game Economy vs Game Finance (Virtual Economy Gamification Tips)
3. Game Economy vs Virtual Economy (Gamification Achievement Systems Tips)
4. Barter System vs Trading System (Virtual Economy Gamification Tips)
5. Tradable Items vs Non-Tradable Items (Virtual Economy Gamification Tips)
6. Virtual Items vs In-Game Items (Gamification Achievement Systems Tips)
7. Virtual Store vs In-Game Store (Virtual Economy Gamification Tips)