[chc]

It comes from the benefit of gaining 10 over the risk of losing one. There exist people who vehemently hate receiving email but for some reason refuse to just opt out, and you will lose them. But they are not the common case. Remember that unless your target market is "a handful of people on HN," you should not place much faith in a self-selected sample of vocal HN users expressing their personal feelings.

Many people here will also tell you that $100 a month is an outrageous price for a service that saves time for software engineers. It is true that they feel that way, but it's a mathematically false statement.