Note that I nowhere said that an iPhone does not leak private information or that Apple cannot get data about the users of their phones. Actually, I am not even sure that the data on the backup is entirely encrypted. One can access contacts and appointments from a web browser, for example.
This being said and since you appear to know what data phones leak, could you run the same analysis for a typical 150$ phone? Consider that most of them, particularly the feature-rich at a knockout price from Asian origin, come with a dubious layer of extra software.