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 $754 — a different platform, not this one.

DeathKeep

An evil Necromancer has escaped from his icy prison and is wreaking havoc upon the surrounding lands. Journey to a bleak, frozen wasteland and put an end to the terror! Be prepared to fight your way through over 25 dungeons - each with 8 floors within! Explore icy caverns, three ominous towers and a fantastic final dungeon! Along the way, you will battle over 30 different monsters - including a variety of Tanar'ri, Mephits and Golems. Avoid treacherous traps; solve mind boggling puzzles. The ability to jump and fly adds a new dimension to your quest - but be careful not to fall! The 3D environment means you can look up, down and all around. Everything you view is in natural perspective - including the beasties that want you dead. You have 3 characters to choose from: a male fighter dwarf, a male half-elf fighter mage, or a female elf mage, each of which give a unique flair to the game. Watch the mood of the game intensify as the cinematics change according to the active character. This is the nostalgia dungeon delving at its best - fast, furious, and fun. DeathKeep will keep you in suspense and terrified for hours!