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 $38K — a different platform, not this one.

Wyvia

The Wyverns are gone... Now your home is plunged into chaos as monsters invade from their world as a new recruit to the mercenary guild you must tackle this threat head on. Without the protection of the wyvern only you stand between them and the destruction of Wyvia. Find the source of the monster invasion, discover where the all wyverns have gone, and unlock the power hidden away in you. Wyvia features fun and simple combat that feels good to utilize! Whack Goopies with a huge axe or fire away with screen clearing abilities! Mix and match skills between 10 distinct classes, allocate points into stats and skills, and create a character that's really your own! Explore a variety of locations from plains, deep caves, spooky forests, and frozen wastes as you struggle against the invasion of monsters in your world and find the source of their intrusion. Use the power of Wyverns to fly, gain new abilities, augment your combat prowess and explore the world around you.