finite limit on flagship market
Flagship handsets are an excessive luxury for many people who make do with cheaper phones that are good enough to do day to day stuff, but it's the usual scenario of selling less "premium" product at a higher margin per item, or more "standard" kit with less margin per item.
There's either a lot of people happy to splash a lot of money on flagship phones (I could buy a decent PC for less than many phones!) or a lot of manufacturers will be struggling to shift enough "flagship" items to make it worthwhile.
I'm on SIM only, for just over 100 quid got (new, not used) 8 core, 3Gb RAM, Marshmallow, dual SIM and separate SD slot phablet size phone - a bit rough and ready and not of "flagship" quality but cheap and cheerful & and no need to insure it as cheap enough to replace if it gets damaged.
Your average (good) independent phone shop will normally have a good range of cheap used stuff - a shame most people use the big name high street outlets instead