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 $2.7M — a different platform, not this one.
Legend of Grimrock
Legend of Grimrock is a dungeon crawling role playing game with an oldschool heart mated with modern execution. A group of prisoners are sentenced to certain death by exile to the secluded Mount Grimrock for vile crimes they may or may not have committed. Unbeknownst to the captives, the mountain is riddled with ancient tunnels, dungeons and tombs built by crumbled civilizations of days long past. If they ever wish to see daylight again and reclaim their freedom, the ragtag group of prisoners must form a team and descend through the mountain, level by level. The game brings back an oldschool challenge with highly tactical real-time combat and grid-based movement, devious hidden switches and secrets as well as deadly traps and horrible monsters. Legend of Grimrock puts an emphasis on puzzles and exploration, and the wits and perception of the player are more important tools than even the sharpest of swords would be. And if you are a hardened dungeon crawling veteran and you crave an extra challenge, you can arm yourself with a stack of grid paper and turn on the Oldschool Mode, which disables the luxury of the automap! Are you ready for some classic dungeon-crawling first person perspective party-based RPG action? Are you ready to venture forth and unravel the mysteries of Mount Grimrock? Use the Dungeon Editor to build entirely new adventures and challenges for other players to solve! Explore a vast network of ancient tunnels, discover secrets, and find a way to survive in the perilous dungeons of Mount Grimrock. Cast spells with runes, craft potions with herbs, and fight murderous monsters with a wide variety of weapons. Create a party of four characters and customize them with different races, classes, skills, and traits. Pure-blooded dungeon crawling game with grid-based movement and thousands of squares, riddled with hidden switches, pressure plates, sliding walls, floating crystals, forgotten altars, trapdoors, and more.