Nickel is also expensive. Usually it's quite a bit more expensive than lithium, but it seems that lithium prices are spiking at the moment. (The amount needed

Nickel is also expensive. Usually it's quite a bit more expensive than lithium, but it seems that lithium prices are spiking at the moment. (The amount needed is also relevant, I'm not sure exactly how much lithium is in lithium ion batteries and how much nickel is NiMH.)