I cant argue with someones’ nan’s facebook feed telling them outright lies, but there is a hell of alot of misinformation being peddled - and not just from anti-EV people. Some very pro-EV people also talk total shit. If you havnt considered it, why not?
Someone at the end of those trades has to do the replacement, which will dictate second-hand car value.
BTW, batteries wear gradually, and a battery with 70% of capacity may be annoying for a car, but is still valuable for stationary energy storage (for solar). To me that’s another optimistic factor that can reduce actual replacement cost.
They will not pass these savings onto you.