Which game is credited with popularizing the 'microtransaction' business model in mainstream gaming that has now become a standard revenue stream in the industry?

The gaming industry has evolved dramatically in its monetization strategies over the years. One particular innovation fundamentally changed how games generate revenue and engage players long-term. Test your knowledge about this transformative business model that has reshaped gaming economies and player experiences across multiple platforms. Do you know which gaming company pioneered this now-ubiquitous feature that generates billions in revenue annually?

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Team Fortress 2 (2007) with its introduction of purchasable cosmetic items
MapleStory (2003) with its virtual currency and avatar customization marketplace
World of Warcraft (2004) with its subscription-based model and in-game services
Farmville (2009) with its energy mechanics and decorative purchases