It doesn't really make sense to talk about a single product from a single supplier when talking about supply and demand. You completely leave out the competition side that drives the whole system.

A single example of gravity not working means the theory of gravity doesn't work, unless you mean that economics should not have scientific scrutiny.

Economics is in a dire state of proving theories right. It only accounts for perfectly rational actors. A famous nobel prize winner was proven wrong in the same year or so and he said his graphs didn't account for it.

iphones dropped in price?

In practical terms, yes. Adjusted for inflation, a modern iPhone costs roughly the same as the ones in prior generations, except now you get a lot more bang for your buck with better battery life, improved camera, etc.

iPhones aren't a monopoly (yet): they have to compete with Android phones still, plus Apple probably prioritizes increasing their marketshare and retaining customers over maximizing profit from iPhone sales. iPhones generate a lot of other profits from things like the app store, not just from the phone sales, so pricing the phones maximally would hurt those.