Either he edited it accordingly, or you guys are weaksauce gamers. I got 11,700 (for those of you who are weaksauce mathematicians as well, that's almost ten times what Zilx figured nobody could possibly get) on my first play-through, and I don't even consider myself that good a gamer.
Seems decent enough to me. Needs variety, powerups, bosses. Have the enemies occasionally drop a POWER powerup, for example, that doubles your damage (or better yet, triples it, so you one-shot kill your enemies). Maybe a Health powerup that repairs any damage you've taken. A Shield powerup that renders you invincible for a certain number of hits or a certain period of time. A bomb powerup wouldn't be a bad idea either -- you can collect up to three of them, and press space to drop one, destroying all enemies on the screen for a few seconds and really racking up the points.
I'd also like to see some variety in the enemies themselves. Maybe have some that actually keep their distance and take evasive action, but fire weapons of their own instead of going all kamikaze. Make those worth more points.
The next step after that, though this would change the game mechanics a lot, would be to add some navigation, maybe with the WASD keys. Throw a barricade in your path, so that you have to move to the appropriate corner to avoid it.
Them's my two cents. Meanwhile, 3/5.