For me it's more the advent of 24 month contracts and higher prices.
Phones are usualy petty much done after 2 years in my experience, either the battery is well past its best or general wear and tear. And I say that as someone who's never cracked a screen and been quite precious about them.
Last high end phone I got was an HTC m8 at launch, they retailed about £600 IIRC or close enough, then a Huawei P9, now an LG G6.
The Huawei was technically the best of those 3 for screen and form factor but the LG has been an absolute trooper, better audio and better battery and comparatively cheaper.
I tend not to buy phones but upgrade my contract.
Used to pay £40 plus per month, now paying £28 I think.
I can't see me buying a phone or long contract where the phone currently retails much more above about £300 or 400. Whilst 'better' they just don't offer me anything that even starts to justify the price.
I suppose if you want a gaming phone that's different, but my use is phone, personal organiser, and Web surfing /Web app access.
If it's got reasonable headphone audio, good battery, and waterproofing that's a plus but that's pretty much standard anyway.