[hiby007]

Well the iOS is so efficient in memory management that every new version of OS they release will run reasonably well on the older phone that Apple supports. Generally iPhone gives 4-5 years of support.

So you need to replace iPhone's less often.

[winternett]

After they were caught for slowing down older devices for years [full disclosure of course].

Android has it's issues, but phone prices should be going downward over time, not up. The core components of most competing phones are mostly made in the same factories now.