Last I checked, not really. It’s $30/month (in my country’s currency) regardless of whether I subscribe via the app or through their website. So at the end of the day, it’s up to the user to decide whether they would like for openAI to get 100% of subscriber revenue (minus payment processing fees) or for a portion of that to go to Apple as well.
I know some services charge you more via the app (to make up for Apple’s 30% cut, such as twitch subs or YouTube premium), but for now at least, chatGPT is jot one of them.