> It has nothing to do with the contract discounts that phone providers used to offer.

It has a lot to do with that. Many US providers offer significant discounts on iPhones when buying them on a (new or renewed) contract. This was a very commonplace thing in Europe as well, but I believe it's become less common.

Installment payments change nothing about the base price.

No, that's true; they don't.

But they still make it much more accessible to buy an iPhone for someone who doesn't have €500 or $1000 or whatever at one time to comfortably spend on one.

The idea that iPhones could be a meaningful "status symbol" by this point in their lifetime, given all the ways one can obtain one cheaply if that is what one wants, and the percentage of people who own them, just doesn't hold up under scrutiny. It's a meme repeated by people who need some reason to believe that people don't buy Apple's products on their own merits—much like the idea that it's a "cult".

You can finance expensive cars too – does that make them any less of a status symbol?

Financing doesn't make anything cheaper relative to its alternatives (given that they can also be financed).

If you can't see the huge difference between "you can pay $1500+/month to own an expensive car" and "you can pay $30/month to own an iPhone" in terms of accessibility, then I'm not sure what to say.