Yeah a lot of apps charge about 30% extra if you subscribe through the app due to the Apple tax. It's best to go to the site directly and see what the actual price is.
I subscribe via apple if at all possible because it sticks all my subs together on one screen. The dates for each are clearly listed. I can unsubscribe from any with a click. The markup is worth all hassle being removed.
I do this with my books - everything from my direct store is a little cheaper. This is because I get a much bigger cut of the royalties selling direct (90-100% minus transaction fees depending on direct sales platform, compared to other storefronts' 30-70%). I also value direct sales a lot because these readers let me bypass a dependency on another middle-man and give me better reach to the customer.
Free YouTube on your phone here with transcripts, audio and videos in landscape, all stored for offline listening, reading and watching https://www.appblit.com/scribe