I think that's true. If you described an early personal computer and its capabilities (including software) in 1970, sure, a lot of people would be "Why would I want that?" But both business people and individuals could probably give some reasonable approximation of what they'd be willing to pay.
The thing with something like a phone is that it's so dependent on several different network effects that it's hard to put a real value on it in isolation. Of course, for an individual device, there's very much an upper limit. I suspect that a lot of people in 1970 would balk at the price of an iPhone but then they had other telecoms charges that would seem extortionate today.
I have a copy of an old humorous computer article in a book to the effect of things that people thought they'd want computers for and how they didn't really play out (given the tech at the time).
Yeah, agreed, an iPhone or really most computers is a difficult comparison to make for this sort of thing. I mean, what is an iPhone anyway? It relies on a lot of infrastructure that wouldn’t be available in the 70’s: the modern internet, the apple App Store, usb chargers, a way to write and compile iOS programs and get it to run them, the first and third party programming ecosystem.
It seems like a nitpick but the value proposition of the thing is very dependent on the ability of all those, I’m sure we all have some intuition of which ought to be included, but it might not match.
An iPhone with all those things would probably be extremely valuable I guess. Thousands of times faster than the fastest supercomputer and a bit easier to carry.
The Blackberry was initially mostly of interest to "important people" whose organizations were paying for easier texting and email on the go. I did eventually get a Treo in 2006 on my own mostly because I was doing some travel on crutches and didn't want to carry a laptop. But the iPhone--especially by a few years post-2007 introduction--was really transformational for a lot of people in the mainstream. But, as you say, that was dependent on a lot of things that weren't inherent in the phone hardware.
Mobile communications for the most part was very much a premium early adopter phenomenon for people who really needed it in some form and/or didn't much care about the cost. Satellite was like that and is only now slowly changing.
The thing with something like a phone is that it's so dependent on several different network effects that it's hard to put a real value on it in isolation. Of course, for an individual device, there's very much an upper limit. I suspect that a lot of people in 1970 would balk at the price of an iPhone but then they had other telecoms charges that would seem extortionate today.