I am not underestimating the work/effort that goes into creating it, I am very aware of the effort required. My primary motivation for using it in the first place was because I was too busy to write something like this myself, and for that the price is fair - my time is worth more right now.
But I don't think a system which sends out email reminders and logs daily text updates is $600 per year software, sorry.
The author is clearly perfectly entitled to keep the price at whatever level he likes, and I wish him all the luck in his endeavour.
1) something useful they need 2) cost is low enough that they don't need to get approval
Keep in mind your dealing with programmers on Hacker News, but most non-programmers don't think anything is necessarily simple or easy to recreate.
Great job, and good luck on future sales.