I don't think it's the case if you take inflation into account.
You could see here: https://www.reddit.com/r/dataisbeautiful/comments/16dr1kb/oc...
new ones are generally cheaper if adjusted for inflation. This is a sale price, but assuming that margins stay the same it should reflect the manufacturing price. And from what I remember about apple earnings their margins increased over time, so it means the new phones are even cheaper. Which kind of makes sense.
I should have addressed this. This thread is about the capital costs of getting to the first sale, so that's model training for an LLM vs all the R&D in an iPhone.
Recent iPhones use Apple's own custom silicon for a number of components, and are generally vastly more complex. The estimates I have seen for iPhone 1 development range from $150 million to $2.5 billion. Even adjusting for inflation, a current iPhone generation costs more than the older versions.
And it absolutely makes sense for Apple to spend more in total to develop successive generations, because they have less overall product risk and larger scale to recoup.