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 $4.8M — a different platform, not this one.

Psychonauts

Delve into people's minds as Raz, a powerful young cadet at a psychic summer camp. While working on his merit badge in levitation, Raz discovers that someone is kidnapping psychic children and stealing their brains. To foil this evil plot and earn the title of Psychonaut, Raz must project himself into the mind of one bizarre character after another to battle their nightmares and inner demons. He does all this while continuing to earn psychic merit badges in subjects such as telekinesis, clairvoyance and fire-starting. This amazing 3D platformer adventure, full of brilliant humor, trippy setting, and surreal action, became famous for its originality and excellence of design. If you're looking for a unique gaming experience, this is a fine pick. More than just fine, as a matter of fact--double fine! A brilliant story that will not let go of you until you finish the game An absolutely unique atmosphere with a psychedelical level design by Tim Schafer's famous Double Fine team One of the greatest titles of the platformer genre