I see apple as like LVMH, but for phones. It has a minority of overall sales, but a majority of the “luxury” part of the market. This gives them influence over the whole market, but not a real monopoly.
They have like 57% of all smartphones (and 100% of the app store) in the USA last I saw. 57% of the market doesn't seem at all limited to just luxury end. Frankly, I can fathom how so many kids even seem to have iPhones given the money involved.