For example, Y Combinator makes zero direct revenue from hosting HN. But I would feel pretty dishonest if I were to claim on that account that it has no effect on our bottom line.
Not every kind of word of mouth matters. HN is not that big of community, and is comprised mostly of certain types of users that either don't care about 37's products, or know about them already anyway.
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.
Why, can't he check for affiliate links?
So the value is at the very least $300 a month, it could be significantly more than that.
Like a whooping $1000 a month?