Even though a significant part of the price increase can be attributed to regular inflation, the highly advanced technical components that are for example built into the iPhone 13 Pro Max are much more expensive to produce in comparison to those in the original iPhone from 2007.
https://www.notebookcheck.net/Apple-s-iPhone-prices-have-skyrocketed-over-the-past-14-years-iPhone-13-is-81-more-expensive-than-the-original-iPhone.572991.0.html
The original iPhone was $499 for a 4 GB version and $599 for a 8 GB version without a contract IIRC. iPhone 13 mini, which is the spiritual successor to the old standard line, is $729 for a 128 GB version. Yes, definitely more expensive. But hardly 81 %. The reason for phones being so expensive is that people keep buying them. Apparently, the price is right.