It will take a good four years to determine how durable the hinge / fold / crease is.
Samsung will also launch a tri-fold soon, it seems: https://www.androidauthority.com/samsung-galaxy-g-fold-exclusive-animation-leak-3573652/
The separate external screen seems like a horribly inelegant solution to me too, but I wonder if a lot of use of the “closed” book mode would result in a visible delineation between that half of the screen and the less-often used half due to OLED wear. A compensation algorithm would of course dim the lesser-used half to try to match, but it would have to be awfully precise to be unnoticeable if the two halves were on one continuous surface. Of course, two separate screens with a bezel/separator in between—a la the Westworld staff tablets—would solve this and a great many other problems…
But your comparison price equivalent has two cellular devices, each with 512GB of storage. Since the foldable iPhone cannot become two separate cellular devices, and, knowing Apple, will probably have a base storage of 256, you should use the price of the base WiFi iPad mini and the price of the Pro Max with 256.
I seldom do things like use Safari or Lightroom in landscape, especial if it's something that uses the keyboard, because the screen isn't tall so I would absolutely like a double height landscape screen. However if all you do with he larger screen is watch movies then sure, it probably doesn't give much value beyond the ProMax.
Comparing against base devices is irrelevant for me because my phone is 512gb and my iPad is 1TB cellular. So a combined device would save me a significant amount of money in iPad upgrades.
And I shouldn't be helping people justify the cost of the rumored foldable iPhone anyhow, as I personally believe that having an iPhone and a separate iPad is the better option considering the state of current display and battery technology.
You're welcome to do whatever you want, but its easy for each person to compare costs of an iPhonebook to what they would spend on their separate devices including iPad storage and cellular upgrades.
You have to price a cellular & Wi-Fi iPad Mini for a far comparison because when you unfold a foldable phone, you have a mini tablet with cellular and Wi-Fi, and also the storage has to be equal as well, like you've mentioned. I've never owned a foldable with less than 512GB of storage and I've owned 9 of them to date. Therefore I used 512 in this example.
Then you're a foldable fan, and unlikely to agree with my rumor era opinion that buying the cellular iPad mini with 512GB and an iPhone Pro Max with 512GB is a better use of the money anyway.
The aspect ratio will be great for content and all media
