No revenue estimate for GOG — its rating/review counts don't calibrate to sales the way Steam's do. The Steam version is estimated at $1.7M — a different platform, not this one.

Mount & Blade

Calradia is a land at war, offering great riches and even greater dangers to adventurers and mercenaries that flock to shed their blood on its soil. With courage and a strong sword, an unknown stranger can make a name as a warrior. Free-form sand-box gameplay. You are free to go anywhere in a world with more than a hundred unique locations including villages, castles and towns. Groundbreaking horseback combat. Highly advanced and intuitive sword-fighting systems. Fight on horseback and foot using a vast variety of medieval weapons, each with unique characteristics. You can be anything from a lonesome adventurer to a commander of armies or an owner of villages, castles or towns. Sophisticated AI will challenge you in combat and in your strategic plans. Freedom to interact with hundreds of characters.