I built a tool that lets you read any article and especially and newsletter on Kindle. I charge $6-$10 monthly or about $60-$85 yearly for it and >150 active su

I built a tool that lets you read any article and especially and newsletter on Kindle. I charge $6-$10 monthly or about $60-$85 yearly for it and >150 active subscribers. The yearly pre-payment that's about 20% cheaper than monthly is by far the most popular plan.