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 $2.1K — a different platform, not this one.

Kalyzmyr

Once the legendary warrior Smyrna, now long forgotten in the depths of Kalyzmyr. Break your chains and earn your freedom! Use your mighty axe and devastate your foes that keep you locked in Kalyzmyr! Fight and defend through hordes of demons in this old-school fast-paced action game. Each floor starts with a defense phase where you defend yourself from hordes of creatures by buying and upgrading defensive equipment. Kill monsters to earn money and experience. Level up your stats and skills, loot chests to level up your equipment using materials. Optimize your build to overcome challanges. Randomized boons that can either boost your strength or weaken you. Feeling weak? Or did you get unlucky? Break the door to turn back to the previous floor anytime. Farm lower levels and be prepared to face stronger opponents. Unleash Your True Power Unleash Smyrna’s true potential by activating ‘Berserk’ mode which allows you to attack at maximum speed for the duration. Challange Bosses You can challange boss of the current level by paying Crystals to the Mushroom King for extra materials. Defeat three bosses and make your escape from the sunless dungeon Kalyzmyr.