The price of iPhone against bitcoin has grown gradually with time. This shows the progress in the value of bitcoin. I've similar experience buying a mobile. I bought a phone for $150, when the price of bitcoin was close around $2000. If I haven't bought a phone by that time now the same value could've got me the costliest mobile phone by now.
Same with me but I don't have any regrets at all because I'm using my phone now for crypto works and its really helpful to have a good phone and beside iPhone last longer compare to any brand this is already proven and tested by me. No matter how expensive iPhones are many are still buying to have and that's a good branding made by Steve same thing with Bitcoin, Satoshi started this one and even if Bitcoin is more expensive now many new investors are still coming it.
^ That wasn't a "gradual" Bitcoin rise actually. It was a rapid growth.
If you take a look at the illustration made by the OP, from the first iPhone it cost around 2,857 to buy one, and eventually reducing the bitcoin value a huge chunk up to this very moment. Take note, iPhone price is increasing as well as Bitcoin price.
On the other hand, I don't believe iPhone is the most durable phone that the other brands. Durability always depends on the user's hands. I also think iPhone belongs to the luxuries, you're not actually paying for the phone features instead you're paying for the brand.