I bought yesterday too; the cost to me for lifetime access was $79.99 AUD, which is about $83 CAD or $52 USD. When I last looked, the full price for this tier of membership was $99 USD.
The regular price is $99.99 US. The sale price is $49.99 US.
In Canada, the regular (non RP) price is $129.99. The sale price is $69.99. Apple sets the price outside of the US using exchange rates and aims for “9.99” at the end when possible, that’s why it’s not 64.99. Apple does not update prices frequently due to exchange rates.
Unfortunately, the App Store does not have the concept of a “sale” (just a price change). As a result, when I change the price, Nitro get a new price, but it doesn’t know what the old price was (and each country has its own price that is specified by Apple). Anyway, I will figure out a way to put better messaging into the pricing screen for Nitro so it’s easier to understand the sale prices. Sorry for the confusing experience.