Wow, that's interesting. $200k per year, that translates to... about 10,000 people buying the full game in a single year, that means about 300 people each and every day?
That's about right, but it's not even every day. On an average day, we sell 20-50 copies, I'd say. Bear in mind that includes sales of the expansions, so while it's 10,000(ish) sales of the game-and-related-stuff per year, it's not quite that many customers, since quite a few buy one or more expansions.
On the flip side, it's actually a lot more copies than just that which are moved, because a lot of them are sold on discount. With a Steam sale, we can move thousands upon thousands of copies in a single day, and with most other vendors or our own site, we can move hundreds of copies in a day, a weekend, or a week with it on discount.
How do they find out about the game? I mean, I am interested in stuff like this (hell, I played the first ever RTS, "Stonkers", when it came out in early 1980s) but I found about A.I. War by pure chance, when desperately browsing on Steam...
It all depends on what you read and when, unfortunately. You can google AI War to see a lot of the various coverage we've had, but places like Rock, Paper Shotgun, Co-Optimus, and Blue's News tend to cover our releases and big events. Other sites do, as well, and we've had tons of reviews (the game was the 40th-best-reviewed PC game of 2009, including AAA games, according to MetaCritic). So when people look at reviews on various sites for various genres, or even on metacritic, they find us. Or looking at our entry on wikipedia, or just googling for strategy games.
Sometimes people just get a hankering for a space RTS, or a space 4X, or a co-op RTS, and they google and find us. Most of our customers seem to find us via either: 1) seeing a discount promotion; 2) reading about us on some forums that other fans are talking about us on; or 3) just finding us in the listings of games on various distribution channels, like you did. Word of mouth has been critical for us, though, and ongoing.
While I have your attention: I use Linux as my primary OS, that means I have to play A.I. War on my "music computer" (the only computer out of 5 that I have Windows installed on and I use it exclusively for composing music - well, I was until I got A.I. War). I originally intended to play A.I. War on Linux, under Wine. It runs without problems but there are big problems with performance, sound and animation is choppy etc... Do you even consider releasing the native Linux version or releasing the main engine source code (excluding audiovisulal assets, for example) under GPL and let other people do the conversion? I have a hunch that Linux people are exactly the people who prefer A.I. War over Starcraft 2...
Unfortunately our hands are pretty tied there, as we use the Unity 3D engine and it's a matter of when they add support for linux directly. We've had other players talking about how the game plays great there under WINE, so it might be a problem with your OpenGL version, driver version, or similar; I'm not sure if anyone plays the game very extensively under linux, though. If Unity ever gets a native linux version of their engine, we'll definitely start doing builds for linux, as well. Fingers crossed!