From these articles, the old Prius NiMH batteries are much cheaper (probably 2k – 5k or so) compared to LIon. The other articles states cost of Lithium Ion at 4-5 times so you’re looking at 10-15k.
Maybe the 3k – 5k isn’t a lot for you, but if anyone wanted to lease a car instead of replacing a bat, there’s a car lease payment right there instead of replacing something. At least the old NiMH batteries do seem to be lasting well, I give you that.
For the newer tech Lithium, there is concern with limited recharges, constant discharges, etc…
Maybe like with those Eneloop batteries, maybe the NiMH tech is just so much more mature to have limited discharge as well as many charge cycles compared to Lithium.