I didn't flag anything, sorry for the drama, but at this point it would be good to provide a link, DOI, authors, title, ... . ChatGPT citations are notoriously unreliable.
I just asked it the same question, and it provided a different answer, and a study that can't be found in google.
Running your own software on your own iPhone requires a $99 a year subscription. Just for code signing, it's basically pure profit, and there's no practical way around it.
It's a classic masterpiece of platform gatekeeping: Getting money for doing nothing, but being the only one who can do it.
I just asked it the same question, and it provided a different answer, and a study that can't be found in google.