I have been looking at leafs with about 80k on them with about 50 mile range left.The experience of heavily cycled Leaf batteries in taxis has been positive on the whole and it would appear that in the lithium batteries used age is really the main driver in deterioration rather than excessive cycling unlike flooded lead acids. PCP cars are limited in contracts by miles travelled, not battery cycles - I'd be amazed if some enterprising off grid users weren't heavily utilising their mobile batteries and storing up with cheap electricity generated elsewhere to be used at home. Shame that most new EVs tend to come now with a technically inferior charging connector (CCS) which doesn't yet do vehicle to grid.
Re taxis, they tend to do a lot of miles in short space of time & I think cycle damage as you hint also takes time to kick in.
The damage has been done but loosing 2% say on 250 miles does not show up as they get charged well before they get to that state of discharge. But after a few years of 2% reduction you suddenly start to see it bite.
Personal I still think that battery damage costs more than the elec you can move from free at work to home use.
Its just that the second or third car owner will be the one paying the price until people catch on & the second hand value drops.
Like I said the cars that are around £5k have 50 miles bats left after reduction in performance due to age / miles. I cant see them actually being worth that much. Will be interesting to see what is selling and what is not. I expect they will either still be for sale in 3 months or price dropped to sell.