The rts Zero-K's code is worth 7.5M$ http://code.google.com/p/zero-k/ plus 4.3 million for SpringRTS engine the game was built on http://www.ohloh.net/p/springrts/estimated_cost. Estimate does not include map, model, sound and AI.
In comparison GoW3 cost 44M$ according to http://www.escapistmagazine.com/news/view/98960-God-of-War-III-Developed-for-44-Million and that in 2005 the mainstream console game cost 3-6M$ http://en.wikipedia.org/wiki/Video_game_development.
Here's a gameplay video. It has catchy music.
Games on the spring engine focus more on features and technical proficiency than graphics, like fully 3D with deformable terrain and 1k+ units ingame. At the moment of posting there are 20 people playing ZK.
In comparison GoW3 cost 44M$ according to http://www.escapistmagazine.com/news/view/98960-God-of-War-III-Developed-for-44-Million and that in 2005 the mainstream console game cost 3-6M$ http://en.wikipedia.org/wiki/Video_game_development.
Here's a gameplay video. It has catchy music.