I believe the comment is intended to point out to HN readers that this algorithm was central to the game, and since the game made a large amount of money, then this algorithm served (at least in part) as a basis for Notch's monetary rewards. I do not believe the comment was meant to suggest that this one algorithm by itself made money, as certainly any reasonable reader would understand that it is the whole game that made money. It is unlikely that the commenter was suggesting that you could, for example, sell a Perlin noise function for a billion dollars, or even generate any revenue directly from the noise function itself, absent a compelling game around it.

The commenter was, I believe (and I say this without having any inside information as to his or her thought process) employing a technique in which the full range of details surrounding an event are ignored in favor of one aspect (here, the Perlin noise function) on which we want to focus.