The paper covers issues of item-selling based payment model(micro-transactions) in Korean online games. Firstly, we characterize two payment models in online game: subscription based payment model and item-selling based payment model. We then investigate and characterize itemselling based payment model in online games and introduce two online games, "Kart Rider" and "Special Force" which have been successfully adapted item-selling based payment model as their business model. Finally, we discuss game design issues to efficiently accommodate item-selling based payment model in online games: how to balance between items obtained by game-money and items purchased by real money, how to abstract the function of such items, and how to strength events and communities. The survey will provide insight of designing micro-transaction policy for the next-generation console markets with "Xbox 360", "Playstation 3", and "Wii" as its major axis.