 "Achaea"s creator Matt Mihaly came up with the idea of a dual currency system to generate revenue to cover the higher operating costs; while one in-game currency remained free, the other premium currency could only be purchased with real-world funds, and many special items could only be purchased with the premium currency.Achaea's controversial revenue structure has received attention from the game development industry.Although Iron Realms Entertainment provides a custom MUD interface for the game, there are neither up-front costs, nor monthly fees typical for the MMORPG-genre.