We can look at the Toyota Prius since it's mass-produced and has both technologies within. The big-ticket item that usually needs fixing as the mileage goes up

We can look at the Toyota Prius since it's mass-produced and has both technologies within. The big-ticket item that usually needs fixing as the mileage goes up is the (nicad) battery pack. Upgrades (lifepo4) are available and cost in the range of $2000. For a battery that's <2kwh. Now scale that up to be able to power an EV and you can see why it's Nissan Leafs that are scrap value once the (admittedly sub-optimally cooled) batteries go.