Almost all e-bike batteries sold to consumers are ridiculously overpriced[1] relative to their components. Especially those from reputable brands like Bosch and Shimano which supplies most of the better e-bike brands on the street.

It’s a combination of having relatively well-off consumers, who lack the time/knowledge to start messing with their expensive machines and lack of generic spare parts due to the likes of Bosch locking down their components, and creating specialised computers (similar to how modern cars work) so that only authorised repair shops can work on them.

[1] https://ampedcycling.com/e-bike-battery-prices-what-can-i-ex...