I am guessing you missed the sale,
Well, on the bright side, it will be 75% off again for the Christmas Steam sale.
(And that's without it being a highlighted game if I recall the last big sale correctly.)
Though there is an Audiosurf 2 coming out,
it might actually have all the features of the first game.
Be part of the answer, not part of the problem.
1 Corinthians 13; remember it always.