There's also a weird thread that runs through most products that actually sell - if it sold, people must be willing to pay more. You'll have to balance 5 people at $5 vs 1 person at $25, and what that's worth to you. So often people tell other entrepreneurs to raise their prices! Raise them again! But there is a sweet spot, and good sales don't mean the price was too low.
I bought Non-app Calendar. I liked what I saw, but I doubt I would have paid more for it. It's a nicely constructed PDF, not a book or game or SaaS or web hosting or any number of other things that cost around or below what I paid for NAC. (Write a companion book on project planning with a fresh take and maybe it would be worth more.)
That's not to say I don't like the product. I really do. I've recommended it to friends and we use it as an exercise tool for planning at the office. So, thanks for the good work, I'm just not sure I'd listen to every opinion that comes your way. :)