It's already under $6K for a LEAF battery replacement. ICE drivers have to drop at least ~8K every 6 years for gasoline and engine maintenance and repair.
And "severely degraded" is -30% capacity, not really severe except in the older lowest-capacity batteries.
Except along with that -30% capacity drop, there is also increased internal resistance in the battery that is also going to affect range (lower miles/kWh). It's not just -30% capacity = -30% range. E.g. this Leaf owner who, after 5 years, had -37% capacity but -50% effective range: https://www.quora.com/What-is-the-life-expectancy-of-a-Nissa...
I won't dispute the $8K/6 years for ICE vehicles (although I am curious if that's legit) but if you look at the savings rate of the average American I think you'll see ICEs' steady expense rate of gas fillups, oil change, etc. suit it better than EVs' lower day-to-day but eventual massive hit.
https://electrek.co/2018/03/26/nissan-leaf-battery-pack-repl...