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 $5.4K — a different platform, not this one.

Slipstream 5000

Feel the speed!   The future. Conventional motor racing has yielded to the advances of thrust drive technology. Popularity for Slipstream racing is at its peak. Successful flyers quickly become icons and heroes. Race fans flock in their millions to the circuit-side stadiums hoping to catch a glimpse of the latest anti-grav machines which defy all laws of motion. The track's prepared, the crowd are hustling for the best seats, and the drivers and commentators are all psyched and hungry for action.   Control many upgradeable futuristic racers under arcade or simulation racing style. Experience high speed aerial moves and dramatic crashes on excellently designed tracks. Feel the speed of the slipstream!   Compete as one of 10 different characters with unique Slipstream aircraft, each with their own features, weapons, and flying style. Fast-paced action, smooth craft controls, and excellent track design. With good old fashion split-screen multiplayer mode, enjoy a retro head-to-head race against a friend.