The prices for in-app purchases - those purchases you make in the app itself - are the retail prices for Ninja Number. Ordering through the app is a seamless process that doesn't require going to a website, signing up, then downloading the app, and logging in.
Ordering through the website, though, does give you 30% off the retail price for your first year's subscription. To get the best pricing, go to https://ninjanumber.com!