Exactly , his post is not objective. Front page of hackers news is essentially word of mouth marketing, which the author(Noah) says matters. Based on the data provided Noah does not know if the HN readers who signed up for the free accounts are recommending the paid services to others. So the value is at the very least $300 a month, it could be significantly more than that. Moreover what effect does the HN traffic have on their advertising, their job board, book sales ? He does not measure, so I doubt the accuracy of his conclusion.