I call bullshit unless you've got some stats from other "mainstream" games that went on sale in that price range. That's the kind or price that idiots would bite on with any game that may have heard of from others. Sorry but I have no faith in humanity, especially not the steam community. Just look at the stats for today, it's back to normal:
Current Players Peak Today Game
49,297 61,787 Team Fortress 2
46,320 55,470 Counter-Strike
40,471 52,554 Counter-Strike: Source
21,669 28,476 Call of Duty: Modern Warfare 2 - Multiplayer
19,094 27,728 Football Manager 2011
15,049 21,687 Call of Duty Black Ops - Multiplayer
14,279 21,311 Sid Meier's Civilization V
8,864 12,347 Left 4 Dead 2
6,558 10,514 Terraria
6,539 9,247 Garry's Mod