if the price is 40% or lower for a new conditioned iphone, it may still be worth if one does not want to spend the 100% price for the same grade of iphone 12 pro max. A12 is still a beast even my A11 on iphone x too. if it is second hand then i will say it is not worth it.

even i can use my iphone 6 plus as a secondary still with no issue. it is a A8 chip. A12 is 4 gen ahead.

iphone xs max comparing to iphone 12 pro max (if assume it is selling at the same starting price this year)
rm2799 vs rm5299
52.82% vs 100%

one brand new condition iphone can easily be used for 5 years. now iphone xs max is only 2 years old so the depreciation should be 40%, while now the depreciation is 47.18% which is actually more than this. it is almost half of the price only and they are only 2 years difference.

if one is buying for their family members such as kids or elderly, it is really not bad deal becos they won't need the latest flagship iphone. and this kind of price can buy two instead of buying iphone 12 pro max. and iphone xs max is still not a bad phone even at now. only bummer here is probably the 64gb storage which can limit the capability of the phone in long run. but if it is for elderly or kids, i think 64gb should still be sufficient for basic usage.

if one is buying for ownself, like myself i am upgrading my iphone x to iphone 12 pro max. then of course i will be better off just buy the upcoming iphone 12 pro max instead.