Treat the battery well (avoid wireless charging when you can, don't charge when hot) and these devices can last a long time. And even when the battery starts to die, you can get an official replacement for much less than the cost of a new phone.

If you're a typical high income tech person who upgrades their desktop, laptop, phone, tablet, and watch on a regular cycle, that's a staggering amount of money to stay on the treadmill. I'm consciously choosing to keep my devices as long as possible. I've given up smartwatches, my desktop and tablet are 8 years old, and I plan to keep my phone for at least 5 years.